Circulating angiotensin converting enzyme 2 activity as a biomarker of silent atherosclerosis in patients with chronic kidney disease

Prognostic value of elevated plasma angiotensin-converting enzyme 2 in cardiometabolic diseases: A review

Angiotensin-converting enzyme 2, as an internal anti regulator of the renin-angiotensin hormone cascade reaction, plays a protective role in vasodilation, inhibition of fibrosis, and initiation of anti-inflammatory and antioxidative stress by degrading angiotensin II and generating angiotensin (1-7). Multiple studies have shown that plasma angiotensin-converting enzyme 2 activity is low in healthy populations without significant cardiometabolic disease, and elevated plasma angiotensin-converting enzyme 2 levels can be used as a novel biomarker of abnormal myocardial structure and/or adverse events in cardiometabolic diseases. This article aims to elaborate the determinants of plasma angiotensin-converting enzyme 2 concentration, the relevance between angiotensin-converting enzyme 2 and cardiometabolic disease risk markers, and its relative importance compared with known cardiovascular disease risk factors. Confronted with the known cardiovascular risk factors, plasma angiotensin-converting enzyme 2 (ACE2) concentration uniformly emerged as a firm predictor of abnormal myocardial structure and/or adverse events in cardiometabolic diseases and may improve the risk prediction of cardiometabolic diseases when combined with other conventional risk factors. Cardiovascular disease is the leading cause of death worldwide, while the renin-angiotensin system is the main hormone cascade system involved in the pathophysiology of cardiovascular disease. A multi-ancestry global cohort study from the general population by Narula et al revealed that plasma ACE2 concentration was strongly associated with cardiometabolic disease and might be an easily measurable indicator of renin-angiotensin system disorder. The association between this atypical hormone disorder marker and cardiometabolic disease is isolated from conventional cardiac risk factors and brain natriuretic peptide, suggesting that a clearer comprehending of the changes in plasma ACE2 concentration and activity may help us to improve the risk prediction of cardiometabolic disease, guide early diagnosis and feasible therapies, and develop and test new therapeutic targets.

Circulating angiotensin converting enzyme 2 and COVID-19

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has triggered a widespread outbreak since December 2019. The SARS-CoV-2 infection-related illness has been dubbed the coronavirus disease 2019 (COVID-19) by the World Health Organization. Asymptomatic and subclinical infections, a severe hyper-inflammatory state, and mortality are all examples of clinical signs. After attaching to the angiotensin converting enzyme 2 (ACE2) receptor, the SARS-CoV-2 virus can enter cells through membrane fusion and endocytosis. In addition to enabling viruses to cling to target cells, the connection between the spike protein (S-protein) of SARS-CoV-2 and ACE2 may potentially impair the functionality of ACE2. Blood pressure is controlled by ACE2, which catalyzes the hydrolysis of the active vasoconstrictor octapeptide angiotensin (Ang) II to the heptapeptide Ang-(1-7) and free L-Phe. Additionally, Ang I can be broken down by ACE2 into Ang-(1-9) and metabolized into Ang-(1-7). Numerous studies have demonstrated that circulating ACE2 (cACE2) and Ang-(1-7) have the ability to restore myocardial damage in a variety of cardiovascular diseases and have anti-inflammatory, antioxidant, anti-apoptotic, and anti-cardiomyocyte fibrosis actions. There have been some suggestions for raising ACE2 expression in COVID-19 patients, which might be used as a target for the creation of novel treatment therapies. With regard to this, SARS-CoV-2 is neutralized by soluble recombinant human ACE2 (hrsACE2), which binds the viral S-protein and reduces damage to a variety of organs, including the heart, kidneys, and lungs, by lowering Ang II concentrations and enhancing conversion to Ang-(1-7). This review aims to investigate how the presence of SARS-CoV-2 and cACE2 are related. Additionally, there will be discussion of a number of potential therapeutic approaches to tip the ACE/ACE-2 balance in favor of the ACE-2/Ang-(1-7) axis.

Plasma Angiotensin Converting Enzyme 2 (ACE2) Activity in Healthy Controls and Patients with Cardiovascular Risk Factors and/or Disease

Angiotensin converting enzyme 2 (ACE2) is an endogenous negative regulator of the renin-angiotensin system, a key factor in the development of cardiovascular disease (CVD). ACE2 is also used by SARS-CoV-2 for host cell entry. Given that COVID-19 is associated with hypercoagulability, it is timely to explore the potential relationship between plasma ACE2 activity and the coagulation profile. In this cross-sectional study, ACE2 activity and global coagulation assays (GCA) including thromboelastography, thrombin, and fibrin generation were measured in adult healthy controls (n = 123; mean age 41 ± 17 years; 35% male) and in patients with cardiovascular risk factors and/or disease (n = 258; mean age 65 ± 14 years; 55% male). ACE2 activity was significantly lower in controls compared to patients with cardiovascular risk factors and/or disease (median 0.10 (0.02, 3.33) vs. 5.99 (1.95, 10.37) pmol/mL/min, p < 0.001). Of the healthy controls, 48% had undetectable ACE2 activity. Controls with detectable ACE2 had lower maximum amplitude (p < 0.001). In patients with cardiovascular risk factors and/or disease, those in the 3rd tertile were older and male (p = 0.002), with a higher Framingham grade and increased number of cardiovascular risk factors (p < 0.001). In conclusion, plasma ACE2 activity is undetectable to very low in young healthy controls with minimal clinically relevant associations to GCA. Patients with cardiovascular risk factors and/or disease have increased plasma ACE2 activity, suggesting that it may be an important biomarker of endothelial dysfunction and atherosclerosis.

Angiotensin-converting enzyme 2 and transmembrane protease serine 2 in female and male patients with end-stage kidney disease

BACKGROUND

Individuals with chronic kidney disease are affected by acute respiratory syndrome coronavirus 2 (SARS-CoV-2) due to multiple comorbidities and altered immune system. The first step of the infection process is the binding of SARS-CoV-2 with angiotensin-converting enzyme 2 (ACE2) receptor, followed by its priming by transmembrane protease serine 2 (TMPRSS2). We hypothesized that circulating soluble ACE2 levels, as well as the expressions of ACE2 and TMPRSS2 in the microvasculature, are increased in patients with end-stage kidney disease (ESKD).

METHODS

A total of 210 participants were enrolled, representing 80 ESKD patients and 73 non-CKD controls for soluble ACE2, and 31 ESKD and 26 non-CKD controls for vasculature and fat tissue bioassays. We have assessed ACE2 expression in blood using ELISA and in tissue using immunofluorescence.

RESULTS

Soluble ACE2 levels were higher in ESKD patients compared to controls; however, there is no sex difference observed. In ESKD and controls, soluble ACE2 positively correlated with Interleukin 6 (IL-6) and C-reactive protein (CRP), respectively. Similarly, ACE2 tissue expression in the vasculature was higher in ESKD patients; moreover, this higher ACE2 expression was observed only in male ESKD patients. In addition, TMPRSS2 expression was observed in vessels from males and females but showed no sex difference. The expression of ACE2 receptor was higher in ESKD patients on ACE-inhibitor/angiotensin blocker treatment.

CONCLUSION

ESKD is associated with increased ACE2 levels in the circulation and pronounced in male vasculature; however, further studies are warranted to assess possible sex differences on specific treatment regime(s) for different comorbidities present in ESKD.

The Need for Individualized Risk Assessment in Cardiovascular Disease

Cardiovascular disease remains the leading cause of death in the era of modern medicine despite major advancements in this field. Current available clinical surrogate markers and blood tests do not adequately predict individual risk of cardiovascular disease. A more precise and sophisticated tool that can reliably predict the thrombosis and bleeding risks at an individual level is required in order for clinicians to confidently recommend early interventions with a favorable risk–benefit profile. Critical to the development of this tool is the assessment and understanding of Virchow’s triad and its complex interactions between hypercoagulability, endothelial dysfunction and vessel flow, a fundamental concept to the development of thrombosis. This review explores the pathophysiology of cardiovascular disease stemming from the triad of factors and how individualized risk assessment can be improved through the multimodal use of tools such as global coagulation assays, endothelial biomarkers and vessel flow assessment.

Higher Soluble ACE2 Levels and Increased Risk of Infection-Related Hospitalization in Patients on Maintenance Hemodialysis

Background

Angiotensin-converting enzyme 2 (ACE2) works as an endogenous counter-regulator of the renin-angiotensin system, which has pivotal roles in preventing both cardiovascular disease (CVD) and inflammation. In general populations, higher plasma soluble ACE2 levels were reported to be associated with increased risks of all-cause death and major CVD. Because infections are fatal in patients on maintenance hemodialysis, we aimed to explore whether soluble ACE2 levels are associated with an increased risk of infection-related hospitalization in these patients.

Methods

Using data from a prospective, multicenter, cohort study conducted in Tokyo, Japan, we performed a post-hoc analyses of 724 clinically stable patients on maintenance hemodialysis. We measured baseline serum soluble ACE2 levels and assessed potential determinants of its with infection-related hospitalization as a primary outcome as well as all-cause death and CVD as secondary outcomes using a Cox proportional hazards model.

Results

The soluble ACE2 level (median, 0.16 ng/ml; interquartile range, 0.07–0.57 ng/ml) showed a weak negative association with age. During a median follow-up of 39 months, 106 patients (14.6%) were hospitalized with infectious diseases. Compared with the lower half of soluble ACE2 levels, the higher half was associated with an increased risk of infection-related hospitalization (hazard ratio, 1.57; 95% confidence interval, 1.02–2.41) with adjustment by other risk factors. On the other hand, there were no significant associations between soluble ACE2 and risks of all-cause death and CVD.

Conclusion

Higher soluble ACE2 levels may associate with an increased risk of infection-related hospitalization in patients on maintenance hemodialysis.

Association of renin–angiotensin system blockers with COVID-19 diagnosis and prognosis in patients with hypertension: a population-based study

Background

The effect of renin–angiotensin system (RAS) blockade either by angiotensin-converting enzyme inhibitors (ACEis) or angiotensin-receptor blockers (ARBs) on coronavirus disease 2019 (COVID-19) susceptibility, mortality and severity is inadequately described. We examined the association between RAS blockade and COVID-19 diagnosis and prognosis in a large population-based cohort of patients with hypertension (HTN).

Methods

This is a cohort study using regional health records. We identified all individuals aged 18–95 years from 87 healthcare reference areas of the main health provider in Catalonia (Spain), with a history of HTN from primary care records. Data were linked to COVID-19 test results, hospital, pharmacy and mortality records from 1 March 2020 to 14 August 2020. We defined exposure to RAS blockers as the dispensation of ACEi/ARBs during the 3 months before COVID-19 diagnosis or 1 March 2020. Primary outcomes were: COVID-19 infection and severe progression in hospitalized patients with COVID-19 (the composite of need for invasive respiratory support or death). For both outcomes and for each exposure of interest (RAS blockade, ACEi or ARB) we estimated associations in age-, sex-, healthcare area- and propensity score-matched samples.

Results

From a cohort of 1 365 215 inhabitants we identified 305 972 patients with HTN history. Recent use of ACEi/ARBs in patients with HTN was associated with a lower 6-month cumulative incidence of COVID-19 diagnosis {3.78% [95% confidence interval (CI) 3.69–3.86%] versus 4.53% (95% CI 4.40–4.65%); P &lt; 0.001}. In the 12 344 patients with COVID-19 infection, the use of ACEi/ARBs was not associated with a higher risk of hospitalization with need for invasive respiratory support or death [OR = 0.91 (0.71–1.15); P = 0.426].

Conclusions

RAS blockade in patients with HTN is not associated with higher risk of COVID-19 infection or with a worse progression of the disease.

SARS-CoV-2 Infection Modulates ACE2 Function and Subsequent Inflammatory Responses in Swabs and Plasma of COVID-19 Patients

Angiotensin converting enzyme 2 (ACE2) is a host ectopeptidase and the receptor for the SARS-CoV-2 virus, albeit virus-ACE2 interaction goes far beyond viral entry into target cells. Controversial data exists linking viral infection to changes in ACE2 expression and function, which might influence the subsequent induction of an inflammatory response. Here, we tested the significance of soluble ACE2 enzymatic activity longitudinally in nasopharyngeal swabs and plasma samples of SARS-CoV-2 infected patients, along with the induction of inflammatory cytokines. Release of soluble functional ACE2 increases upon SARS-CoV-2 infection in swabs and plasma of infected patients, albeit rapidly decreasing during infection course in parallel with ACE2 gene expression. Similarly, SARS-CoV-2 infection also induced the expression of inflammatory cytokines. These changes positively correlated with the viral load. Overall, our results demonstrate the existence of mechanisms by which SARS-CoV-2 modulates ACE2 expression and function, intracellular viral sensing and subsequent inflammatory response, offering new insights into ACE2 dynamics in the human upper respiratory tract and pointing towards soluble ACE2 levels as a putative early biomarker of infection severity.

ACE2 Is an Adjacent Element of Atherosclerosis and COVID-19 Pathogenesis

COVID-19 is a highly contagious new infection caused by the single-stranded RNA Sars-CoV-2 virus. For the first time, this infection was recorded in December 2019 in the Chinese province of Wuhan. The virus presumably crossed the interspecies barrier and passed to humans from a bat. Initially, the disease was considered exclusively in the context of damage to the respiratory system, but it quickly became clear that the disease also entails serious consequences from various systems, including the cardiovascular system. Among these consequences are myocarditis, myocardial damage, subsequent heart failure, myocardial infarction, and Takotsubo syndrome. On the other hand, clinical data indicate that the presence of chronic diseases in a patient aggravates the course and outcome of coronavirus infection. In this context, the relationship between COVID-19 and atherosclerosis, a condition preceding cardiovascular disease and other disorders of the heart and blood vessels, is particularly interesting. The renin-angiotensin system is essential for the pathogenesis of both coronavirus disease and atherosclerosis. In particular, it has been shown that ACE2, an angiotensin-converting enzyme 2, plays a key role in Sars-CoV-2 infection due to its receptor activity. It is noteworthy that this enzyme is important for the normal functioning of the cardiovascular system. Disruptions in its production and functioning can lead to various disorders, including atherosclerosis.

Myoglobin and C-reactive protein are efficient and reliable early predictors of COVID-19 associated mortality

Since the emergence of SARS-CoV-2, numerous studies have been attempting to determine biomarkers, which could rapidly and efficiently predict COVID-19 severity, however there is lack of consensus on a specific one. This retrospective cohort study is a comprehensive analysis of the initial symptoms, comorbidities and laboratory evaluation of patients, diagnosed with COVID-19 in Huoshenshan Hospital, Wuhan, from 4th February to 12th March, 2020. Based on the data collected from 63 severely ill patients from the onset of symptoms till the full recovery or demise, we found not only age (average 70) but also blood indicators as significant risk factors associated with multiple organ failure. The blood indices of all patients showed hepatic, renal, cardiac and hematopoietic dysfunction with imbalanced coagulatory biomarkers. We noticed that the levels of LDH (85%, P < .001), HBDH (76%, P < .001) and CRP (65%, P < .001) were significantly elevated in deceased patients, indicating hepatic impairment. Similarly, increased CK (15%, P = .002), Cre (37%, P = 0.102) and CysC (74%, P = 0.384) indicated renal damage. Cardiac injury was obvious from the significantly elevated level of Myoglobin (52%, P < .01), Troponin-I (65%, P = 0.273) and BNP (50%, P = .787). SARS-CoV-2 disturbs the hemolymphatic system as WBC# (73%, P = .002) and NEUT# (78%, P < .001) were significantly elevated in deceased patients. Likewise, the level of D-dimer (80%, P < .171), PT (87%, P = .031) and TT (57%, P = .053) was elevated, indicating coagulatory imbalances. We identified myoglobin and CRP as specific risk factors related to mortality and highly correlated to organ failure in COVID-19 disease.

Angiotensin-converting enzyme 2 and COVID-19: patients, comorbidities, and therapies

On March 11, 2020, the World Health Organization declared coronavirus disease 2019 (COVID-19) a pandemic, and the reality of the situation has finally caught up to the widespread reach of the disease. The presentation of the disease is highly variable, ranging from asymptomatic carriers to critical COVID-19. The availability of angiotensin-converting enzyme 2 (ACE2) receptors may reportedly increase the susceptibility and/or disease progression of COVID-19. Comorbidities and risk factors have also been noted to increase COVID-19 susceptibility. In this paper, we hereby review the evidence pertaining to ACE2's relationship to common comorbidities, risk factors, and therapies associated with the susceptibility and severity of COVID-19. We also highlight gaps of knowledge that require further investigation. The primary comorbidities of respiratory disease, cardiovascular disease, renal disease, diabetes, obesity, and hypertension had strong evidence. The secondary risk factors of age, sex, and race/genetics had limited-to-moderate evidence. The tertiary factors of ACE inhibitors and angiotensin II receptor blockers had limited-to-moderate evidence. Ibuprofen and thiazolidinediones had limited evidence.

ACE2 Is a Prognostic Biomarker and Associated with Immune Infiltration in Kidney Renal Clear Cell Carcinoma: Implication for COVID-19

Background

KIRC is one of the most common cancers with a poor prognosis. ACE2 was involved in tumor angiogenesis and progression in many malignancies. The role of ACE2 in KIRC is still ambiguous.

Methods

Various bioinformatics analysis tools were investigated to evaluate the prognostic value of ACE2 and its association with immune infiltration in KIRC.

Results

ACE2 was shown to be downregulated in KIRC at the mRNA and protein level. Low expression of ACE2 protein in KIRC patients was observed in subgroup analyses based on gender, age, weight, tumor grade, and cancer stage. Upregulation of ACE2 in KIRC was associated with a favorable prognosis. ACE2 mRNA expression showed a positive correlation with the abundance of immune cells (B cells, CD8+ T cells, macrophages, neutrophils, and dendritic cells) and the level of immune markers of different immune cells in KIRC. ACE2 expression could affect, in part, the immune infiltration and the advanced cancer stage. Moreover, enrichment analysis revealed that ACE2 in KIRC were mainly involved in translation factor activity, immunoglobulin binding, metabolic pathways, transcriptional misregulation in cancerous cells, cell cycle, and ribosomal activity. Several ACE2-associated kinases, miRNA, and transcription factor targets in KIRC were also identified.

Conclusion

ACE2 was downregulated in KIRC and served as a prognostic biomarker. It was also shown to be associated with immune infiltration.

Effect of bariatric surgery on cardiac structure and function in obese patients: Role of the renin-angiotensin system

Echocardiographic alterations have been described in obesity, but their modifications after bariatric surgery (BS) and mechanisms are little known, mostly in normotensive patients. We aimed to analyze cardiac changes 1 year post‐BS and to explore possible mechanisms. A cohort of patients with severe obesity (58% normotensives) were prospectively recruited and examined before surgery and after 12 months. Clinical and echocardiographic data, 24 h BP, renin‐angiotensin‐aldosterone system (RAAS) components, cytokines, and inflammatory markers were analyzed at these two time points. Overall reduction in body weight was mean (IQR) = 30.0% (25.9–33.8). There were statistically significant decreases in left ventricle mass index^2.7(LVMI)^2.7, septum thickness (ST), posterior wall thickness (PWT), relative wall thickness (RWT), and E/e’, both in the whole cohort and in patients without RAAS blockers (p ≤ .04 for all). Plasma renin activity (PRA) decreased from (median, IQR) = 0.8 (0.3;1.35) to 0.4 (0.2;0.93) ng/ml/h, plasma aldosterone from 92 (58.6;126) to 68.1 (56.2;83.4) ng/dl, and angiotensin‐converting enzyme (ACE)‐2 activity from 7.7 (5.7;11.8) to 6.8 (5.3;11.2) RFU/µl/h, p < .05. The body weight loss correlated with a decrease in both 24 h SBP and 24 h DBP (Pearson's coefficient 0.353, p = .022 and 0.384, p = .012, respectively). Variation (Δ) of body weight correlated with ΔE/e’ (Pearson's coeff. 0.414, p = .008) and with Δ lateral e’ (Pearson's coeff. = −0.363, p = .018). Generalized linear models showed that ΔPRA was an independent variable for the final (12‐months post‐BS) LVMI^2.7 (p = .028). No other changes in cardiac parameters correlated with ΔBP. In addition to the respective baseline value, final values of PWT and RWT were dependent on 12‐month Δ of PRA, ACE, and ACE/ACE2 (p < .03 for all). We conclude that there are cardiac changes post‐BS in patients with severe obesity, normotensives included. Structural changes appear to be related to modifications in the renin‐angiotensin axis.

ACE2, angiotensin 1-7 and skeletal muscle: review in the era of COVID-19

Angiotensin converting enzyme-2 (ACE2) is a multifunctional transmembrane protein recently recognised as the entry receptor of the virus causing COVID-19. In the renin–angiotensin system (RAS), ACE2 cleaves angiotensin II (Ang II) into angiotensin 1-7 (Ang 1-7), which is considered to exert cellular responses to counteract the activation of the RAS primarily through a receptor, Mas, in multiple organs including skeletal muscle. Previous studies have provided abundant evidence suggesting that Ang 1-7 modulates multiple signalling pathways leading to protection from pathological muscle remodelling and muscle insulin resistance. In contrast, there is relatively little evidence to support the protective role of ACE2 in skeletal muscle. The potential contribution of endogenous ACE2 to the regulation of Ang 1-7-mediated protection of these muscle pathologies is discussed in this review. Recent studies have suggested that ACE2 protects against ageing-associated muscle wasting (sarcopenia) through its function to modulate molecules outside of the RAS. Thus, the potential association of sarcopenia with ACE2 and the associated molecules outside of RAS is also presented herein. Further, we introduce the transcriptional regulation of muscle ACE2 by drugs or exercise, and briefly discuss the potential role of ACE2 in the development of COVID-19.

Angiotensin-converting enzyme 2 (ACE2) levels in relation to risk factors for COVID-19 in two large cohorts of patients with atrial fibrillation

Aims

The global COVID-19 pandemic is caused by the SARS-CoV-2 virus entering human cells using angiotensin-converting enzyme 2 (ACE2) as a cell surface receptor. ACE2 is shed to the circulation, and a higher plasma level of soluble ACE2 (sACE2) might reflect a higher cellular expression of ACE2. The present study explored the associations between sACE2 and clinical factors, cardiovascular biomarkers, and genetic variability.

Methods and results

Plasma and DNA samples were obtained from two international cohorts of elderly patients with atrial fibrillation (n = 3999 and n = 1088). The sACE2 protein level was measured by the Olink Proteomics^® Multiplex CVD II^96 × 96 panel. Levels of the biomarkers high-sensitive cardiac troponin T (hs-cTnT), N-terminal probrain natriuretic peptide (NT-proBNP), growth differentiation factor 15 (GDF-15), C-reactive protein, interleukin-6, D-dimer, and cystatin-C were determined by immunoassays. Genome-wide association studies were performed by Illumina chips. Higher levels of sACE2 were statistically significantly associated with male sex, cardiovascular disease, diabetes, and older age. The sACE2 level was most strongly associated with the levels of GDF-15, NT-proBNP, and hs-cTnT. When adjusting for these biomarkers, only male sex remained associated with sACE2. We found no statistically significant genetic regulation of the sACE2 level.

Conclusions

Male sex and clinical or biomarker indicators of biological ageing, cardiovascular disease, and diabetes are associated with higher sACE2 levels. The levels of GDF-15 and NT-proBNP, which are associated both with the sACE2 level and a higher risk for mortality and cardiovascular disease, might contribute to better identification of risk for severe COVID-19 infection.

Twenty years of progress in angiotensin converting enzyme 2 and its link to SARS-CoV-2 disease

The virulence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the aggressive nature of the disease has transformed the universal pace of research in the desperate attempt to seek effective therapies to halt the morbidity and mortality of this pandemic. The rapid sequencing of the SARS-CoV-2 virus facilitated identification of the receptor for angiotensin converting enzyme 2 (ACE2) as the high affinity binding site that allows virus endocytosis. Parallel evidence that coronavirus disease 2019 (COVID-19) disease evolution shows greater lethality in patients with antecedent cardiovascular disease, diabetes, or even obesity questioned the potential unfavorable contribution of angiotensin converting enzyme (ACE) inhibitors or angiotensin II (Ang II) receptor blockers as facilitators of adverse outcomes due to the ability of these therapies to augment the transcription of Ace2 with consequent increase in protein formation and enzymatic activity. We review, here, the specific studies that support a role of these agents in altering the expression and activity of ACE2 and underscore that the robustness of the experimental data is associated with weak clinical long-term studies of the existence of a similar regulation of tissue or plasma ACE2 in human subjects.

Viral replication of SARS-CoV-2 could be self-limitative - The role of the renin-angiotensin system on COVID-19 pathophysiology

Currently, the world is suffering with one of the biggest pandemics of recent history. Caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the coronavirus disease 2019 (COVID-19) is provoking devastating consequences on economic and social fields throughout all continents. Therefore, pathophysiological knowledge about COVID-19 is imperative for better planning of preventive measures, diagnosis, and therapeutics of the disease. Based on previous studies, this work proposes new hypothesis related to the role of the renin-angiotensin system on the pathophysiology of COVID-19, and its purpose is to enrich the discussion and to offer alternative ways for experimental and clinical studies aiming at the formulation of new diagnosis and/or treatment methods.

Role of Renin-Angiotensin System Components in Atherosclerosis: Focus on Ang-II, ACE2, and Ang-1-7

Atherosclerosis is the leading cause of vascular disease worldwide and contributes significantly to deaths from cardiovascular complications. There is a remarkably close relationship between atherosclerotic plaque formation and the activation of renin-angiotensin system (RAS). However, depending on which RAS pathway is activated, pro- or anti-atherogenic outcomes may be observed. This brief review focuses on the role of three of the most important pieces of RAS axis, angiotensin II (Ang-II), angiotensin converting enzyme type 2 (ACE2), and angiotensin 1-7 (Ang-1-7) and their involvement in atherosclerosis. We focused on the effects of these molecules on vascular function and inflammation, which are important determinants of atherogenesis. Furthermore, we highlighted potential pharmacological approaches to treat this disorder.

Biomarkers associated with COVID-19 disease progression

The coronavirus disease 2019 (COVID-19) pandemic is a scientific, medical, and social challenge. The complexity of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is centered on the unpredictable clinical course of the disease that can rapidly develop, causing severe and deadly complications. The identification of effective laboratory biomarkers able to classify patients based on their risk is imperative in being able to guarantee prompt treatment. The analysis of recently published studies highlights the role of systemic vasculitis and cytokine mediated coagulation disorders as the principal actors of multi organ failure in patients with severe COVID-19 complications. The following biomarkers have been identified: hematological (lymphocyte count, neutrophil count, neutrophil-lymphocyte ratio (NLR)), inflammatory (C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), procalcitonin (PCT)), immunological (interleukin (IL)-6 and biochemical (D-dimer, troponin, creatine kinase (CK), aspartate aminotransferase (AST)), especially those related to coagulation cascades in disseminated intravascular coagulation (DIC) and acute respiratory distress syndrome (ARDS). New laboratory biomarkers could be identified through the accurate analysis of multicentric case series; in particular, homocysteine and angiotensin II could play a significant role.

Angiotensin-converting enzyme 2 influences pancreatic and renal function in diabetic mice

Type 1 diabetes is a T-cell mediated autoimmune disease characterized by pancreatic beta cells destruction. Angiotensin-converting enzyme 2 (ACE2), a component of renin-angiotensin system (RAS) has been identified in pancreas from type 2 diabetic mice and its overexpression prevents beta cell dysfunction. We studied the effect of ACE2 deletion on pancreatic and renal function in the nonobese diabetic mice, a model that mimics type 1 diabetes. ACE2-deficient NOD mice and the respective controls were generated. Pancreas function and immunohistochemistry studies were performed. Renal function and RAS gene expression were also analyzed. Renal proximal tubular cells were obtained from these animals to dissect the effect of ACE2 deficiency in these cells. In NOD mice, ACE2 deletion significantly worsened glucose homeostasis, decreased islet insulin content, increased beta cell oxidative stress, and RIPK1-positive islets as compared with control mice. Angiotensin-converting enzyme and angiotensin II type 1 receptor (AT1R) were also increased in ACE2-deficient mice. In kidneys of 30-day diabetic mice, ACE2 deletion decreased podocyte number within the glomeruli, and altered renal RAS gene expression in tubules. ACE2 deletion influenced the expression of fibrosis-related genes in isolated primary renal proximal tubular cells before diabetes onset in NOD mice. Our findings suggest that ACE2 deletion may have a deleterious impact on beta cell and renal function, by promoting oxidative stress and increasing necroptosis mediators. In addition, this effect is accompanied by RAS alterations in both pancreas and renal proximal tubular cells, indicating that ACE2 may exert a renopancreatic protective effect on type 1 diabetes, which is activated before diabetes starts.

Hypertension and related diseases in the era of COVID-19: a report from the Japanese Society of Hypertension Task Force on COVID-19

Coronavirus disease-2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has affected more than seven million people worldwide, contributing to 0.4 million deaths as of June 2020. The fact that the virus uses angiotensin-converting enzyme (ACE)-2 as the cell entry receptor and that hypertension as well as cardiovascular disorders frequently coexist with COVID-19 have generated considerable discussion on the management of patients with hypertension. In addition, the COVID-19 pandemic necessitates the development of and adaptation to a “New Normal” lifestyle, which will have a profound impact not only on communicable diseases but also on noncommunicable diseases, including hypertension. Summarizing what is known and what requires further investigation in this field may help to address the challenges we face. In the present review, we critically evaluate the existing evidence for the epidemiological association between COVID-19 and hypertension. We also summarize the current knowledge regarding the pathophysiology of SARS-CoV-2 infection with an emphasis on ACE2, the cardiovascular system, and the kidney. Finally, we review evidence on the use of antihypertensive medication, namely, ACE inhibitors and angiotensin receptor blockers, in patients with COVID-19.

Alteration and association between serum ACE2/ angiotensin(1-7)/Mas axis and oxidative stress in chronic kidney disease: A pilot study

Activation of the renin angiotensin system and renal oxidative stress (OS) are critical contributors in the progression of chronic kidney disease(CKD). Recent studies have confirmed that the angiotensin-converting enzyme 2-angiotensin (1-7)-Mas(ACE2/Ang(1-7)/Mas) axis, the important components of renin angiotensin system, protected kidneys against damage by antagonizing angiotensin II and attenuating OS in rats with several nephropathy models, but its effect needs to be further evaluated in clinic. In this study, we aimed to detected serum ACE2/Ang (1-7)/Mas axis, OS conditions and described its clinical associations in patients with CKD at different stages.A total of 48 patients with CKD and 6 healthy controls (CT) were enrolled, and serum angiotensin converting enzyme (ACE), ACE2, Ang (1-7), 8-hydroxy-2'-deoxyguanosine (8-OHdG) were determined by ELISA. Serum extracellular glutathione peroxidase(eGSH-Px) activity and renal functions were determined by the biochemical method.Serum ACE and ACE2 levels in CKD stages 3 to 5 and serum Ang(1-7) levels in CKD stages 4 to 5 without Ang II receptor blockers treatment significantly increased compared to those in the CT group. However, ACE2 was decreased and Ang(1-7) level increased in early CKD stage with Ang II receptor blockers treatment. Higher serum 8-OHdG levels and lower eGSH-Px activity were noted in CKD stages 4 to 5. Serum 8-OHdG level was correlated with serum ACE2, Ang(1-7) expression. Estimated glomerular filtration rate (eGFR) was correlated with serum ACE, ACE2, Ang(1-7), 8-OHdG, Hcy levels and serum eGSH-Px activity. Multiple-regression analysis eGFR was predicted by ACE, Hcy, eGSH-Px, and also can be predicted by ACE2, Ang(1-7), Hcy in CT subgroup.The ACE2/Ang(1-7)/Mas axis is associated with OS, and both them were associated with eGFR in the progression of CKD. Activation of ACE2/Ang(1-7)/Mas axis may have renoprotective effect and can be a potential therapeutic target in patients with early CKD stages.

Inhibition of the P2X7 receptor improves renal function via renin-angiotensin system and nitric oxide on diabetic nephropathy in rats

AIM

To evaluate the effects of P2X₇ receptor blockade on renin-angiotensin system (RAS) in rats with diabetic nephropathy (DN).

MAIN METHODS

Wistar rats were unilaterally nephrectomized and received streptozotocin for diabetes mellitus (DM) induction; control animals (CTL) received the drug vehicle. The animals were submitted to P2X₇ receptor silencing, forming the group (DM + siRNA). The animals were placed in metabolic cages for data collection and evaluation of renal function; at the end of the protocol, the kidney was removed for analysis of P2X₇, renin, angiotensin-converting enzyme (ACE), ACE2, angiotensin, thiobarbituric acid reactive substance levels (TBARS), nitric oxide (NO) and qualitative histological.

KEY FINDINGS

The metabolic profile was attenuated in DM + siRNA vs. DM and there was a significant improvement in creatinine, urea and proteinuria levels in the same group. Renin expression was significantly decreased in DM + siRNA vs. DM. ACE and ACE2 were significantly reduced in DM + siRNA vs. DM. TBARS levels were decreased and NO showed an increase in DM + siRNA vs. DM, both significant. All histological alterations were improved in DM + siRNA vs. DM.

SIGNIFICANCE

Data have shown that although silencing of the P2X₇ receptor did not decrease fasting glucose, it promoted an improvement in the metabolic profile and a significant recovery of renal function, revealing a protective action by the inhibition of this receptor. This effect must have occurred due to the inhibition of RAS and the increase of NO, suggesting that the use of P2X₇ receptors inhibitors could be used as adjuvant therapy against DN progression.

Atherosclerosis in Chronic Kidney Disease: More, Less, or Just Different?

Patients with chronic kidney disease (CKD) are at an increased risk of premature mortality, mainly from cardiovascular causes. The association between CKD on hemodialysis and accelerated atherosclerosis was described >40 years ago. However, more recently, it has been suggested that the increase in atherosclerosis risk is actually observed in early CKD stages, remaining stable thereafter. In this regard, interventions targeting the pathogenesis of atherosclerosis, such as statins, successful in the general population, have failed to benefit patients with very advanced CKD. This raises the issue of the relative contribution of atherosclerosis versus other forms of cardiovascular injury such as arteriosclerosis or myocardial injury to the increased cardiovascular risk in CKD. In this review, the pathophysiogical contributors to atherosclerosis in CKD that are shared with the general population, or specific to CKD, are discussed. The NEFRONA study (Observatorio Nacional de Atherosclerosis en NEFrologia) prospectively assessed the prevalence and progression of subclinical atherosclerosis (plaque in vascular ultrasound), confirming an increased prevalence of atherosclerosis in patients with moderate CKD. However, the adjusted odds ratio for subclinical atherosclerosis increased with CKD stage, suggesting a contribution of CKD itself to subclinical atherosclerosis. Progression of atherosclerosis was closely related to CKD progression as well as to the baseline presence of atheroma plaque, and to higher phosphate, uric acid, and ferritin and lower 25(OH) vitamin D levels. These insights may help design future clinical trials of stratified personalized medicine targeting atherosclerosis in patients with CKD. Future primary prevention trials should enroll patients with evidence of subclinical atherosclerosis and should provide a comprehensive control of all known risk factors in addition to testing any additional intervention or placebo.

Angiotensin-converting enzyme 2 and renal disease

PURPOSE OF REVIEW

The renin-angiotensin system (RAS) is a pivotal player in the physiology and pathophysiology of cardiovascular and renal systems. Discovery of angiotensin-converting enzyme 2 (ACE2), capable of cleaving RAS effector peptide angiotensin (Ang) II into biologically active Ang-(1-7), has increased the complexity of our knowledge of the RAS. ACE2 expression is abundant in the kidney and is thought to provide protection against injury. This review emphasizes current experimental and clinical findings that examine ACE2 in the context of kidney injury and its potential therapeutic impact for treatment of kidney disease.

RECENT FINDINGS

Clinical studies have reported upregulation of ACE2 in urine from diabetic patients, which may be reflective of pathological shedding of renal ACE2 as suggested by mechanistic experiments. Studies in experimental models have investigated the feasibility of pharmacological induction of ACE2 for improvement of renal function, inflammation, and fibrosis.

SUMMARY

Emerging concepts about the RAS indicate that ACE2 is a critical regulator of angiotensin peptide metabolism and the pathogenesis of renal disease. Human recombinant ACE2 is available and may be a practical clinical approach to enzyme replacement. Elucidating precise roles of ACE2 throughout disease progression will enrich our view of the RAS and help identify novel targets and appropriate strategies for intervention.

Elevated plasma angiotensin converting enzyme 2 activity is an independent predictor of major adverse cardiac events in patients with obstructive coronary artery disease. PLoS One. 2018;13:e0198144. [PMID: 29897923 PMCID: PMC5999069 DOI: 10.1371/journal.pone.0198144]

Background

Angiotensin converting enzyme 2 (ACE2) is an endogenous regulator of the renin angiotensin system. Increased circulating ACE2 predicts adverse outcomes in patients with heart failure (HF), but it is unknown if elevated plasma ACE2 activity predicts major adverse cardiovascular events (MACE) in patients with obstructive coronary artery disease (CAD).

Methods

We prospectively recruited patients with obstructive CAD (defined as ≥50% stenosis of the left main coronary artery and/or ≥70% stenosis in ≥ 1 other major epicardial vessel on invasive coronary angiography) and measured plasma ACE2 activity. Patients were followed up to determine if circulating ACE2 activity levels predicted the primary endpoint of MACE (cardiovascular mortality, HF or myocardial infarction).

Results

We recruited 79 patients with obstructive coronary artery disease. The median (IQR) plasma ACE2 activity was 29.3 pmol/ml/min [21.2–41.2]. Over a median follow up of 10.5 years [9.6–10.8years], MACE occurred in 46% of patients (36 events). On Kaplan-Meier analysis, above-median plasma ACE2 activity was associated with MACE (log-rank test, p = 0.035) and HF hospitalisation (p = 0.01). After Cox multivariable adjustment, log ACE2 activity remained an independent predictor of MACE (hazard ratio (HR) 2.4, 95% confidence interval (CI) 1.24–4.72, p = 0.009) and HF hospitalisation (HR: 4.03, 95% CI: 1.42–11.5, p = 0.009).

Conclusions

Plasma ACE2 activity independently increased the hazard of adverse long-term cardiovascular outcomes in patients with obstructive CAD.

Association of FGF-2 Concentrations with Atheroma Progression in Chronic Kidney Disease Patients

BACKGROUND AND OBJECTIVES

Atherosclerosis is highly prevalent in CKD. The rate of progression of atherosclerosis is associated with cardiovascular events. Fibroblast growth factor 2 (FGF-2) is a member of the FGF family with potentially both protective and deleterious effects in the development of atherosclerosis. The role of circulating FGF-2 levels in the progression of atherosclerosis in CKD is unknown.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We used a multicenter, prospective, observational cohorts study of 481 patients with CKD. We determined the presence of atheroma plaque in ten arterial territories by carotid and femoral ultrasounds. Progression of atheromatosis was defined as an increase in the number of territories with plaque after 24 months. Plasma levels of FGF-2 were measured by multiplex analysis. A multivariable logistic regression analysis was performed to determine whether plasma FGF-2 levels were associated with atheromatosis progression.

RESULTS

Average age of the population was 61 years. The percentage of patients in each CKD stage was 51% in stage 3, 41% in stages 4-5, and 8% in dialysis. A total of 335 patients (70%) showed plaque at baseline. Atheromatosis progressed in 289 patients (67%). FGF-2 levels were similar between patients with or without plaque at baseline (79 versus 88 pg/ml), but lower in patients with atheromatosis progression after 2 years (78 versus 98 pg/ml; P<0.01). In adjusted analyses, higher plasma FGF-2 was associated with lower risk of atheromatosis progression (odds ratio [OR], 0.86; 95% confidence interval [95% CI], 0.76 to 0.96; per 50 pg/ml increment). Analysis of FGF-2 in tertiles showed that atheroma progression was observed for 102 participants in the lowest tertile of FGF-2 (reference group), 86 participants in the middle tertile of FGF-2 (adjusted OR, 0.70; 95% CI, 0.40 to 1.20), and 74 participants in the lowest tertile of FGF-2 (adjusted OR, 0.48; 95% CI, 0.28 to 0.82).

CONCLUSIONS

Low FGF-2 levels are independently associated with atheromatosis progression in CKD.

Combination of biomarkers of vascular calcification and sTWEAK to predict cardiovascular events in chronic kidney disease

BACKGROUND AND AIMS

Vascular calcification (VC) and atherosclerosis are associated with an increased cardiovascular morbimortality in chronic kidney disease (CKD). Osteoprotegerin (OPG) and osteopontin (OPN) are involved in both VC and CKD. Soluble tumor necrosis factor-like weak inducer of apoptosis (sTWEAK) has been related to cardiovascular disease. We hypothesized that OPG, OPN and sTWEAK levels may be associated with a higher prevalence of cardiovascular outcomes in patients with CKD.

METHODS

The presence of calcified or non-calcified atherosclerotic plaques was assessed in 1043 stage 3 to 5D CKD patients from The NEFRONA Study. Biochemical measurements and OPG, OPN and sTWEAK serum levels were analyzed. Patients were followed for cardiovascular outcomes (41 ± 16 months).

RESULTS

At recruitment, 26% of CKD patients had VC. The adjusted odds ratios for having VC were 2.22 (1.32-3.75); p=.003 for OPG, and 0.45 (0.24-0.84); p=.01 for sTWEAK concentrations. After follow-up, 95 CV events occurred. In a Cox model, patients with OPG or OPN above and sTWEAK below their optimal cut-off points had an adjusted higher risk of cardiovascular events [HR: 2.10 (1.49-3.90); p=.02; 1.65 (1.02-2.65); p=.04; 2.05 (1.28-3.29), p=.003; respectively]. When CKD patients were grouped according to the number of biomarkers above (OPG and OPN) or below (sTWEAK) their cut-off points, the combination of these biomarkers showed the highest risk for cardiovascular events [HR: 9.46 (3.80-23.5) p < .001]. A composite score of these three biomarkers increased the C-statistic and net reclassification index beyond conventional risk factors and VC.

CONCLUSIONS

The combination of OPG, OPN and sTWEAK increased the predictability of cardiovascular outcomes.

New perspectives on CKD-induced dyslipidemia

INTRODUCTION

Chronic kidney disease (CKD) is a world-wide health concern associated with a significantly higher cardiovascular morbidity and mortality. One of the principal cardiovascular risk factors is the lipid profile. CKD patients have a more frequent and progressive atheromatous disease that cannot be explained by the classical lipid parameters used in the daily clinical practice. Areas covered: The current review summarizes prevailing knowledge on the role of lipids in atheromathosis in CKD patients, including an overview of lipoprotein metabolism highlighting the CKD-induced alterations. Moreover, to obtain information beyond traditional lipid parameters, new state-of-the-art technologies such as lipoprotein subfraction profiling and lipidomics are also reviewed. Finally, we analyse the potential of new lipoprotein subclasses as therapeutic targets in CKD. Expert opinion: The CKD-induced lipid profile has specific features distinct from the general population. Besides quantitative alterations, renal patients have a plethora of qualitative lipid alterations that cannot be detected by routine determinations and are responsible for the excess of cardiovascular risk. New parameters, such as lipoprotein particle number and size, together with new biomarkers obtained by lipidomics will personalize the management of these patients. Therefore, nephrologists need to be aware of new insights into lipoprotein metabolism to improve cardiovascular risk assessment.

Sympathetic Overactivity in Chronic Kidney Disease: Consequences and Mechanisms

The incidence of chronic kidney disease (CKD) is increasing worldwide, with more than 26 million people suffering from CKD in the United States alone. More patients with CKD die of cardiovascular complications than progress to dialysis. Over 80% of CKD patients have hypertension, which is associated with increased risk of cardiovascular morbidity and mortality. Another common, perhaps underappreciated, feature of CKD is an overactive sympathetic nervous system. This elevation in sympathetic nerve activity (SNA) not only contributes to hypertension but also plays a detrimental role in the progression of CKD independent of any increase in blood pressure. Indeed, high SNA is associated with poor prognosis and increased cardiovascular morbidity and mortality independent of its effect on blood pressure. This brief review will discuss some of the consequences of sympathetic overactivity and highlight some of the potential pathways contributing to chronically elevated SNA in CKD. Mechanisms leading to chronic sympathoexcitation in CKD are complex, multifactorial and to date, not completely understood. Identification of the mechanisms and/or signals leading to sympathetic overactivity in CKD are crucial for development of effective therapeutic targets to reduce the increased cardiovascular risk in this patient group.

Characterization of ACE and ACE2 Expression within Different Organs of the NOD Mouse

Renin angiotensin system (RAS) is known to play a key role in several diseases such as diabetes, and renal and cardiovascular pathologies. Its blockade has been demonstrated to delay chronic kidney disease progression and cardiovascular damage in diabetic patients. In this sense, since local RAS has been described, the aim of this study is to characterize angiotensin converting enzyme (ACE) and ACE2 activities, as well as protein expression, in several tissues of the non-obese diabetic (NOD) mice model. After 21 or 40 days of diabetes onset, mouse serums and tissues were analyzed for ACE and ACE2 enzyme activities and protein expression. ACE and ACE2 enzyme activities were detected in different tissues. Their expressions vary depending on the studied tissue. Thus, whereas ACE activity was highly expressed in lungs, ACE2 activity was highly expressed in pancreas among the studied tissues. Interestingly, we also observed that diabetes up-regulates ACE mainly in serum, lung, heart, and liver, and ACE2 mainly in serum, liver, and pancreas. In conclusion, we found a marked serum and pulmonary alteration in ACE activity of diabetic mice, suggesting a common regulation. The increase of ACE2 activity within the circulation in diabetic mice may be ascribed to a compensatory mechanism of RAS.