ACE2 deficiency modifies renoprotection afforded by ACE inhibition in experimental diabetes

Bibliometric and visual analysis of ACE2/Ang 1-7/MasR axis in diabetes and its microvascular complications from 2000 to 2023

Background

The pathogenesis of diabetes and its microvascular complications are intimately associated with renin angiotensin system dysregulation. Evidence suggests the angiotensin converting enzyme 2 (ACE2)/angiotensin 1-7 (Ang 1-7)/Mas receptor (MasR) axis regulates metabolic imbalances, inflammatory responses, reduces oxidative stress, and sustains microvascular integrity, thereby strengthening defences against diabetic conditions. This study aims to conduct a comprehensive analysis of the ACE2/Ang 1-7/MasR axis in diabetes and its microvascular complications over the past two decades, focusing on key contributors, research hotspots, and thematic trends.

Methods

This cross-sectional bibliometric analysis of 349 English-language publications was performed using HistCite, VOSviewer, CiteSpace, and Bibliometrix R for visualization and metric analysis. Primary analytical metrics included publication count and keyword trend dynamics.

Results

The United States, contributing 105 articles, emerged as the most productive country, with the University of Florida leading institutions with 18 publications. Benter IF was the most prolific author with 14 publications, and Clinical Science was the leading journal with 13 articles. A total of 151 of the 527 author's keywords with two or more occurrences clustered into four major clusters: diabetic microvascular pathogenesis, metabolic systems, type 2 diabetes, and coronavirus infections. Keywords such as "SARS", "ACE2", "coronavirus", "receptor" and "infection" displayed the strongest citation bursts. The thematic evolution in this field expanded from focusing on the renin angiotensin system (2002-2009) to incorporating ACE2 and diabetes metabolism (2010-2016). The latter period (2017-2023) witnessed a significant surge in diabetes research, reflecting the impact of COVID-19 and associated conditions such as diabetic retinopathy and cardiomyopathy.

Conclusions

This scientometric study offers a detailed analysis of the ACE2/Ang 1-7/MasR axis in diabetes and its microvascular complications, providing valuable insights for future research directions.

Clinical and preclinical evidence that angiotensin-converting enzyme inhibitors and angiotensin receptor blockers prevent diabetic peripheral neuropathy

Given possible involvement of the central and peripheral angiotensin system in pain processing, we conducted clinical and preclinical studies to test whether pharmacological inhibition of the angiotensin system would prevent diabetic peripheral neuropathy (DPN) accompanying type 2 diabetes mellitus (T2DM). In the preclinical study, the nociceptive sensitivity was determined in leptin-deficient ob/ob mice, a T2DM model. A clinical retrospective cohort study was conducted, using the medical records of T2DM patients receiving antihypertensives at three hospitals for nearly a decade. In the ob/ob mice, daily treatment with perindopril, an angiotensin-converting enzyme inhibitor (ACEI), or telmisartan, an angiotensin receptor blocker (ARB), but not amlodipine, an L-type calcium channel blocker (CaB), significantly inhibited DPN development without affecting the hyperglycemia. In the clinical study, the enrolled 7464 patients were divided into three groups receiving ACEIs, ARBs and the others (non-ACEI, non-ARB antihypertensives). Bonferroni's test indicated significantly later DPN development in the ARB and ACEI groups than the others group. The multivariate Cox proportional analysis detected significant negative association of the prescription of ACEIs or ARBs and β-blockers, but not CaBs or diuretics, with DPN development. Thus, our study suggests that pharmacological inhibition of the angiotensin system is beneficial to prevent DPN accompanying T2DM.

The RAAS Goodfellas in Cardiovascular System

In the last two decades, the study of the renin-angiotensin-aldosterone system (RAAS) has revealed a counterregulatory protective axis. This protective arm is characterized by ACE2/Ang 1-7/MasR and Ang 1-9 that largely counteracts the classic arm of the RAAS mediated by ACE/Ang II/AT1R/aldosterone and plays an important role in the prevention of inflammation, oxidative stress, hypertension, and cardiovascular remodeling. A growing body of evidence suggests that enhancement of this counterregulatory arm of RAAS represents an important therapeutic approach to facing cardiovascular comorbidities. In this review, we provide an overview of the beneficial effects of ACE2, Ang 1-7/MasR, and Ang 1-9 in the context of oxidative stress, vascular dysfunction, and organ damage.

Could Systemic Inflammatory Index Predict Diabetic Kidney Injury in Type 2 Diabetes Mellitus?

BACKGROUND

The systemic inflammatory index (SII) is a new inflammatory marker that has been the subject of various studies in diseases with chronic inflammation. Diabetic nephropathy is a disease associated with chronic inflammation. We aimed to evaluate the relationship between SII and diabetic nephropathy.

METHODS

Patients with diabetes who applied to our outpatient clinic were included in the study. Diabetic patients were divided into two groups: those with diabetic nephropathy and those without. In addition, healthy individuals who applied to our clinic for general check-ups during these dates were included as the control group. The SII values and other characteristics of the three study groups were compared.

RESULTS

The median SII value for those with DKI was 584 (178-4819); for those without DKI, it was 282 (64-618); and for the control group, it was 236 (77.5-617) (p < 0.001). SII was significantly and positively correlated with BMI, weight, blood glucose, HbA1c, CRP, and creatinine, and negatively correlated with the glomerular filtration rate (GFR) value. SII values higher than 336 have 75% sensitivity and 70% specificity in detecting DKI.

CONCLUSION

The SII value can predict diabetic kidney injury in diabetics, and it can be used as an adjunctive diagnostic tool.

Human ACE2 expression, a major tropism determinant for SARS-CoV-2, is regulated by upstream and intragenic elements

Angiotensin-converting enzyme 2 (ACE2), part of the renin-angiotensin system (RAS), serves as an entry point for SARS-CoV-2, leading to viral proliferation in permissive cell types. Using mouse lines in which the Ace2 locus has been humanized by syntenic replacement, we show that regulation of basal and interferon induced ACE2 expression, relative expression levels of different ACE2 transcripts, and sexual dimorphism in ACE2 expression are unique to each species, differ between tissues, and are determined by both intragenic and upstream promoter elements. Our results indicate that the higher levels of expression of ACE2 observed in the lungs of mice relative to humans may reflect the fact that the mouse promoter drives expression of ACE2 in populous airway club cells while the human promoter drives expression in alveolar type 2 (AT2) cells. In contrast to transgenic mice in which human ACE2 is expressed in ciliated cells under the control of the human FOXJ1 promoter, mice expressing ACE2 in club cells under the control of the endogenous Ace2 promoter show a robust immune response after infection with SARS-CoV-2, leading to rapid clearance of the virus. This supports a model in which differential expression of ACE2 determines which cell types in the lung are infected, and this in turn modulates the host response and outcome of COVID-19.

RAGE pathway activation and function in chronic kidney disease and COVID-19

The multi-ligand receptor for advanced glycation end-products (RAGE) and its ligands are contributing factors in autoimmunity, cancers, and infectious disease. RAGE activation is increased in chronic kidney disease (CKD) and coronavirus disease 2019 (COVID-19). CKD may increase the risk of COVID-19 severity and may also develop in the form of long COVID. RAGE is expressed in essentially all kidney cell types. Increased production of RAGE isoforms and RAGE ligands during CKD and COVID-19 promotes RAGE activity. The downstream effects include cellular dysfunction, tissue injury, fibrosis, and inflammation, which in turn contribute to a decline in kidney function, hypertension, thrombotic disorders, and cognitive impairment. In this review, we discuss the forms and mechanisms of RAGE and RAGE ligands in the kidney and COVID-19. Because various small molecules antagonize RAGE activity in animal models, targeting RAGE, its co-receptors, or its ligands may offer novel therapeutic approaches to slowing or halting progressive kidney disease, for which current therapies are often inadequate.

Type 1 diabetes is associated with significant changes of ACE and ACE2 expression in peripheral blood mononuclear cells

BACKGROUND AND AIMS

The renin-angiotensin system (RAS), which is a key mediator of cardiovascular homeostasis, has two main axes. The classic one, including angiotensin-converting enzyme (ACE) and Angiotensin (Ang) II, promoting vasoconstriction, and the "alternative" one, including ACE2 and Ang1-7, with opposed actions to AngII. ACE2 has been identified as the main receptor of SARS-CoV2, whereby it enters the cells, leading to the downregulation of surface ACE2 and RAS tissue unbalance. Given that diabetes is associated with an increase in COVID-19 severity and death, we aimed at evaluating RAS expression in patients with type 1 diabetes (T1D).

METHODS AND RESULTS

This is a case-control study comparing 39 T1D patients to 33 controls, with a median age of 29 and 32 years, and no comorbidities. ACE and ACE2 gene expression was assessed in peripheral blood mononuclear cells. T1D patients had higher ACE expression and circulating AngII, which were related to glucose levels. T1D patients had lower ACE2 expression. However, ACE2 expression was also related to the sex of participants, being higher in the female group. T1D women did not show the same increase of ACE2 expression that was seen in control women.

CONCLUSION

T1D promotes the increase of ACE, AngII, and ACE/ACE2, which might contribute to the higher cardiovascular risk, as well as to severe tissue injury induced by SARS-CoV2 in these patients. The ratio ACE/ACE2 does not differ between men and women with T1D, which might explain why CVD or COVID-19 do not show substantial gender differences in these patients.

Ramipril Reduces Acylcarnitines and Distinctly Increases Angiotensin-Converting Enzyme 2 Expression in Lungs of Rats

The angiotensin-converting enzyme 2 (ACE2) receptor has been identified as the entry receptor for the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that is abundantly expressed in many organs. With respect to the role of circulating ACE2 and its receptor expression in the pathogenesis of the SARS-CoV-2 infection, it is still debated whether diseases such as hypertension or pharmacotherapies, including ACE inhibitors and angiotensin receptor blockers that affect ACE2 receptor expression, may modulate the severity and outcome of the coronavirus disease 2019 (COVID-19). We therefore tested the hypothesis that treatment with the ACE inhibitor Ramipril affects organ-specific ACE2 receptor mRNA and protein expression as well as the serum metabolome in BioBreeding (BB) rats. Twelve male BioBreeding rats were randomly divided into a Ramipril (10 mg/kg body weight) treatment group or a control group (N = 12; n = 6 per group) over a period of seven days. Ramipril treatment resulted in the reduction of acylcarnitines (C3–C6) out of 64 metabolites. Among the different organs studied, only in the lungs did Ramipril treatment significantly increase both Ace2 mRNA and ACE2 receptor membrane protein levels. Increased ACE2 receptor lung expression after Ramipril treatment was not associated with differences in ACE2 serum concentrations between experimental groups. Our data provide experimental in vivo evidence that the ACE inhibitor Ramipril selectively increases pulmonary ACE2 receptor mRNA and protein levels and reduces acylcarnitines.

The mechanism of multiple organ dyfunction syndrome in patients with COVID-19

In late 2019, an outbreak of coronavirus disease 2019 (COVID‐19) arose, caused by severe acute respiratory syndrome coronavirus type 2 (SARS‐CoV‐2). This disease rapidly became a public health event of international concern. In addition to the most typical symptoms of dyspnea, numerous patients with COVID‐19 exhibited systemic symptoms, such as cardiovascular disease, liver and kidney failure, and disorders in coagulation. At present, clinical data indicates that numerous patients who are critically ill die from multiple organ dysfunction syndromes (MODS). Moreover, the entry of SARS‐CoV‐2 into cells causing severe pathology and progressive organ failure is precisely mediated by the human angiotensin‐converting enzyme 2 protein. This plays a role in maintaining both fluid and electrolyte homeostasis, ensuring the stability of the internal environment. Therefore, the present review aimed to investigate the pathogenesis of MODS caused by SARS‐CoV‐2 infection based on the current clinical data and previous studies.

Inflammatory factor storm, oxidative stress, and disseminated intravascular coagulation cause multiple organ dysfunction syndromes (MODS) in coronavirus disease 2019 patients.

Angiotensin‐converting enzyme 2 (ACE2) protein, closely related to viral infection, mediates organ damage and causes MODS.

Aging, underlying disease, and obesity downregulate ACE2 and may exacerbate MODS.

Foe and friend in the COVID-19-associated acute kidney injury: an insight on intrarenal renin-angiotensin system

Since the first reported case in December of 2019, the coronavirus disease 2019 (COVID-19) has became an international public health emergency. So far, there are more than 228,206,384 confirmed cases including 4,687,066 deaths. Kidney with high expression of angiotensin-converting enzyme 2 (ACE2) is one of the extrapulmonary target organs affected in patients with COVID-19. Acute kidney injury (AKI) is one of the independent risk factors for the death of COVID-19 patients. The imbalance between ACE2-Ang(1-7)-MasR and ACE-Ang II-AT1R axis in the kidney may contribute to COVID-19-associated AKI. Although series of research have shown the inconsistent effects of multiple common RAS inhibitors on ACE2 expression and enzyme activity, most of the retrospective cohort studies indicated the safety and protective effects of ACEI/ARB in COVID-19 patients. This review article highlights the current knowledge on the possible involvement of intrarenal RAS in COVID-19-associated AKI with a primary focus on the opposing effects of ACE2-Ang(1-7)-MasR and ACE-Ang II-AT1R signaling in the kidney. Human recombinant soluble ACE2 or ACE2 variants with preserved ACE2-enzymatic activity may be the best options to improve COVID-19-associated AKI.

Activation of angiotensin-converting enzyme 2 ameliorates metabolic syndrome-induced renal damage in rats by renal TLR4 and nuclear transcription factor κB downregulation

BACKGROUND

Metabolic syndrome (MetS) is an independent risk factor for chronic kidney disease (CKD) through many mechanisms, including activation of the renin-angiotensin system. The deleterious effects of angiotensin II (Ang II) can be counterbalanced by angiotensin-converting enzyme 2 (ACE2). Diminazene aceturate (DIZE), an anti-trypanosomal drug, can activate ACE2.

OBJECTIVE

This study aimed to investigate the possible reno-protective effects of DIZE in MetS rats with elucidation of related mechanisms.

MATERIALS AND METHODS

Thirty adult male Wistar albino rats were divided equally into control, MetS, and MetS + DIZE groups. Body weight, systolic blood pressure (SBP), and urinary albumin levels were measured. Serum levels of fasting blood glucose (FBG), insulin, uric acid, lipid profile, urea, and creatinine were measured. Homeostasis Model Assessment Index (HOMA-IR) was estimated. Subsequently, renal levels of ACE2, Ang II, malondialdehyde (MDA), reduced glutathione (GSH), and tumor necrosis factor-α (TNF-α) were measured with histopathological and immunohistochemical assessment of TLR4 and NF-κB in renal tissues.

RESULTS

MetS caused dyslipidemia with significant increases in body weight, SBP, FBG, serum insulin, HOMA-IR, uric acid, urea, creatinine, urinary albumin, and renal levels of Ang II, MDA, and TNF-α, whereas renal ACE2 and GSH were significantly decreased. Renal TLR4 and NF-κB immunoreactivity in MetS rats was upregulated. DIZE supplementation of MetS rats induced significant improvements in renal function parameters; this could be explained by the ability of DIZE to activate renal ACE2 and decrease renal Ang II levels with downregulation of renal TLR4 and NF-κB expression.

CONCLUSION

DIZE exerts a reno-protective effect in MetS, mainly by downregulating renal TLR4 and NF-κB levels.

Prognostic Factors for COVID-19 Hospitalized Patients with Preexisting Type 2 Diabetes

BACKGROUND

Type 2 diabetes (T2D) as a worldwide chronic disease combined with the COVID-19 pandemic prompts the need for improving the management of hospitalized COVID-19 patients with preexisting T2D to reduce complications and the risk of death. This study aimed to identify clinical factors associated with COVID-19 outcomes specifically targeted at T2D patients and build an individualized risk prediction nomogram for risk stratification and early clinical intervention to reduce mortality.

METHODS

In this retrospective study, the clinical characteristics of 382 confirmed COVID-19 patients, consisting of 108 with and 274 without preexisting T2D, from January 8 to March 7, 2020, in Tianyou Hospital in Wuhan, China, were collected and analyzed. Univariate and multivariate Cox regression models were performed to identify specific clinical factors associated with mortality of COVID-19 patients with T2D. An individualized risk prediction nomogram was developed and evaluated by discrimination and calibration.

RESULTS

Nearly 15% (16/108) of hospitalized COVID-19 patients with T2D died. Twelve risk factors predictive of mortality were identified. Older age (HR = 1.076, 95% CI = 1.014-1.143, p=0.016), elevated glucose level (HR = 1.153, 95% CI = 1.038-1.28, p=0.0079), increased serum amyloid A (SAA) (HR = 1.007, 95% CI = 1.001-1.014, p=0.022), diabetes treatment with only oral diabetes medication (HR = 0.152, 95%CI = 0.032-0.73, p=0.0036), and oral medication plus insulin (HR = 0.095, 95%CI = 0.019-0.462, p=0.019) were independent prognostic factors. A nomogram based on these prognostic factors was built for early prediction of 7-day, 14-day, and 21-day survival of diabetes patients. High concordance index (C-index) was achieved, and the calibration curves showed the model had good prediction ability within three weeks of COVID-19 onset.

CONCLUSIONS

By incorporating specific prognostic factors, this study provided a user-friendly graphical risk prediction tool for clinicians to quickly identify high-risk T2D patients hospitalized for COVID-19.

Angiotensin-converting enzyme 2: a key enzyme in key organs

2020 marked the 20th anniversary of the discovery of the angiotensin-converting enzyme 2 (ACE2). This major event that changed the way we see the renin-angiotensin system today could have passed quietly. Instead, the discovery that ACE2 is a major player in the severe acute respiratory syndrome coronavirus 2 pandemic has blown up the literature regarding this enzyme. ACE2 connects the classical arm renin-angiotensin system, consisting mainly of angiotensin II peptide and its AT1 receptor, with a protective arm, consisting mainly of the angiotensin 1-7 peptide and its Mas receptor. In this brief article, we have reviewed the literature to describe how ACE2 is a key protective arm enzyme in the function of many organs, particularly in the context of brain and cardiovascular function, as well as in renal, pulmonary and digestive homeostasis. We also very briefly review and refer to recent literature to present an insight into the role of ACE2 in determining the course of coronavirus diseases 2019.

Which ones, when and why should renin-angiotensin system inhibitors work against COVID-19?

The article describes the possible pathophysiological origin of COVID-19 and the crucial role of renin-angiotensin system (RAS), providing several “converging” evidence in support of this hypothesis. SARS-CoV-2 has been shown to initially upregulate ACE2 systemic activity (early phase), which can subsequently induce compensatory responses leading to upregulation of both arms of the RAS (late phase) and consequently to critical, advanced and untreatable stages of COVID-19 disease. The main and initial actors of the process are ACE2 and ADAM17 zinc-metalloproteases, which, initially triggered by SARS-CoV-2 spike proteins, work together in increasing circulating Ang 1–7 and Ang 1–9 peptides and downstream (Mas and Angiotensin type 2 receptors) pathways with anti-inflammatory, hypotensive and antithrombotic activities. During the late phase of severe COVID-19, compensatory secretion of renin and ACE enzymes are subsequently upregulated, leading to inflammation, hypertension and thrombosis, which further sustain ACE2 and ADAM17 upregulation. Based on this hypothesis, COVID-19-phase-specific inhibition of different RAS enzymes is proposed as a pharmacological strategy against COVID-19 and vaccine-induced adverse effects. The aim is to prevent the establishment of positive feedback-loops, which can sustain hyperactivity of both arms of the RAS independently of viral trigger and, in some cases, may lead to Long-COVID syndrome.

Overexpression of angiotensin-converting enzyme 2 by renin-angiotensin system inhibitors. Truth or myth? A systematic review of animal studies

Angiotensin-converting enzyme 2 (ACE2) protects against organ damage in hypertension and cardiovascular diseases by counter regulating the renin-angiotensin system (RAS). ACE2 is also the receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Based on the claim that RAS inhibitors (RASIs) cause ACE2 overexpression in some animal experiments, concerns have arisen that RASIs may aggravate SARS-CoV-2 infection and coronavirus disease-2019 severity in RASI-treated patients. To achieve a comprehensive review, a systematic search of MEDLINE/PubMed was conducted regarding the effects of RASIs on tissue ACE2 mRNA/protein expression in healthy animals and animal models of human diseases. We identified 88 eligible articles involving 168 experiments in the heart, kidneys, lungs, and other organs. Three of 38 experiments involving healthy animals showed ACE2 expression greater than twice that of the control (overexpression). Among 102 disease models (130 experiments), baseline ACE2 was overexpressed in 16 models (18 experiments) and less than half the control level (repression) in 28 models (40 experiments). In 72 experiments, RASIs did not change ACE2 levels from the baseline levels of disease models. RASIs caused ACE2 overexpression compared to control levels in seven experiments, some of which were unsupported by other experiments under similar conditions. In 36 experiments, RASIs reversed or prevented disease-induced ACE2 repression, yielding no or marginal changes. Therefore, ACE2 overexpression appears to be a rare rather than common consequence of RASI treatment in healthy animals and disease models. Future studies should clarify the pathophysiological significance of RASI-induced reversal or prevention of ACE2 repression in disease models.

Lock, Stock and Barrel: Role of Renin-Angiotensin-Aldosterone System in Coronavirus Disease 2019

Since the end of 2019, the medical-scientific community has been facing a terrible pandemic caused by a new airborne viral agent known as SARS-CoV2. Already in the early stages of the pandemic, following the discovery that the virus uses the ACE2 cell receptor as a molecular target to infect the cells of our body, it was hypothesized that the renin-angiotensin-aldosterone system was involved in the pathogenesis of the disease. Since then, numerous studies have been published on the subject, but the exact role of the renin-angiotensin-aldosterone system in the pathogenesis of COVID-19 is still a matter of debate. RAAS represents an important protagonist in the pathogenesis of COVID-19, providing the virus with the receptor of entry into host cells and determining its organotropism. Furthermore, following infection, the virus is able to cause an increase in plasma ACE2 activity, compromising the normal function of the RAAS. This dysfunction could contribute to the establishment of the thrombo-inflammatory state characteristic of severe forms of COVID-19. Drugs targeting RAAS represent promising therapeutic options for COVID-19 sufferers.

New perspectives on angiotensin-converting enzyme 2 and its related diseases

Since the worldwide outbreak of coronavirus disease 2019, angiotensin-converting enzyme 2 (ACE2) has received widespread attention as the cell receptor of the severe acute respiratory syndrome coronavirus 2 virus. At the same time, as a key enzyme in the renin-angiotensin-system, ACE2 is considered to be an endogenous negative regulator of vasoconstriction, proliferation, fibrosis, and proinflammation caused by the ACE-angiotensin II-angiotensin type 1 receptor axis. ACE2 is now implicated as being closely connected to diabetes, cardiovascular, kidney, and lung diseases, and so on. This review covers the available information on the host factors regulating ACE2 and discusses its role in a variety of pathophysiological conditions in animal models and humans.

Plasma ACE2 predicts outcome of COVID-19 in hospitalized patients

AIMS

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) binds to angiotensin converting enzyme 2 (ACE2) enabling entrance of the virus into cells and causing the infection termed coronavirus disease of 2019 (COVID-19). Here, we investigate associations between plasma ACE2 and outcome of COVID-19.

METHODS AND RESULTS

This analysis used data from a large longitudinal study of 306 COVID-19 positive patients and 78 COVID-19 negative patients (MGH Emergency Department COVID-19 Cohort). Comprehensive clinical data were collected on this cohort, including 28-day outcomes. The samples were run on the Olink® Explore 1536 platform which includes measurement of the ACE2 protein. High admission plasma ACE2 in COVID-19 patients was associated with increased maximal illness severity within 28 days with OR = 1.8, 95%-CI: 1.4-2.3 (P < 0.0001). Plasma ACE2 was significantly higher in COVID-19 patients with hypertension compared with patients without hypertension (P = 0.0045). Circulating ACE2 was also significantly higher in COVID-19 patients with pre-existing heart conditions and kidney disease compared with patients without these pre-existing conditions (P = 0.0363 and P = 0.0303, respectively).

CONCLUSION

This study suggests that measuring plasma ACE2 is potentially valuable in predicting COVID-19 outcomes. Further, ACE2 could be a link between COVID-19 illness severity and its established risk factors hypertension, pre-existing heart disease and pre-existing kidney disease.

Diabetic kidney disease in type 2 diabetes: a review of pathogenic mechanisms, patient-related factors and therapeutic options

The global prevalence of diabetic kidney disease is rapidly accelerating due to an increasing number of people living with type 2 diabetes. It has become a significant global problem, increasing human and financial pressures on already overburdened healthcare systems. Interest in diabetic kidney disease has increased over the last decade and progress has been made in determining the pathogenic mechanisms and patient-related factors involved in the development and pathogenesis of this disease. A greater understanding of these factors will catalyse the development of novel treatments and influence current practice. This review summarises the latest evidence for the factors involved in the development and progression of diabetic kidney disease, which will inform better management strategies targeting such factors to improve therapeutic outcomes in patients living with diabetes.

Should We Be Concerned about the Association of Diabetes Mellitus and Periodontal Disease in the Risk of Infection by SARS-CoV-2? A Systematic Review and Hypothesis

The objective of this article was to conduct a systematic review of the literature to contrast the existing evidence regarding the relationship between periodontal disease (PD) and diabetes mellitus (DM) with the possibly increased risk of SARS-CoV-2 infection, as well as to establish a hypothesis that explains the ways in which this interaction could take place. A literature search up from 1 January 2020 to 21 March 2021 was conducted in three electronic databases, namely, PubMed, Web of Science, and Scopus, in order to identify studies on periodontal disease alone or in conjunction with diabetes mellitus, reporting any relation with SARS-CoV-2 infection as a primary outcome. Only articles published in the English language were included. Due to the lack of studies, we decided to collect all the theoretical and clinical evidence suggesting a possible biological pathway evidencing the relationship among PD, DM, and SARS-CoV-2 infection. From a total of 29 articles, 12 were included for final review studies (five reviews, two hypotheses, one Special Issue, one perspective, one commentary, one case–control study, and one case report). In addition, this systematic review article hypothesizes the correlation between PD and type 2 diabetes mellitus (T2DM) by expression of angiotensin-converting enzyme 2 (ACE2) in periodontal tissue and the risk of SARS-CoV-2 infection. T2DM is a metabolic disorder characterized by high blood glucose levels resulting from altered insulin secretion or action. Likewise, periodontitis and T2DM are inflammatory disorders with a bidirectional association, and both diseases have a similar immunomodulatory cascade and cytokine profile. ACE2 is a crucial component of the renin–angiotensin system (RAS) and the key factor of entry in the cells by the new SARS-CoV-2. ACE2 is widely distributed in the lung and kidneys, and interestingly has a great distribution in the oral cavity, principally in the tongue and periodontal tissue. ACE2 in periodontal tissue plays a crucial role between health and disease. Moreover, the ACE2/Ang-(1-7)/MasR axis is downregulated in the dysbiotic and inflammatory periodontal environment. Nevertheless, the balance of ACE2 activity is modified in the context of concurrent diabetes, increasing the expression of ACE2 by the uncontrolled glycemia chronic in T2DM. Therefore, the uncontrolled hyperglycemia possibly increases the risk of developing periodontitis and triggering overexpression of ACE2 in periodontal tissue of T2DM patients, with these events potentially being essential to SARS-CoV-2 infection and the development of mild-to-severe form of COVID-19. In this sense, we would like to point out that the need for randomized controlled trials is imperative to support this association.

A comprehensive guide to the pharmacologic regulation of angiotensin converting enzyme 2 (ACE2), the SARS-CoV-2 entry receptor

The recent emergence of coronavirus disease-2019 (COVID-19) as a global pandemic has prompted scientists to address an urgent need for defining mechanisms of disease pathology and treatment. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent for COVID-19, employs angiotensin converting enzyme 2 (ACE2) as its primary target for cell surface attachment and likely entry into the host cell. Thus, understanding factors that may regulate the expression and function of ACE2 in the healthy and diseased body is critical for clinical intervention. Over 66% of all adults in the United States are currently using a prescription drug and while earlier findings have focused on possible upregulation of ACE2 expression through the use of renin angiotensin system (RAS) inhibitors, mounting evidence suggests that various other widely administered drugs used in the treatment of hypertension, heart failure, diabetes mellitus, hyperlipidemias, coagulation disorders, and pulmonary disease may also present a varied risk for COVID-19. Specifically, we summarize mechanisms on how heparin, statins, steroids and phytochemicals, besides their established therapeutic effects, may also interfere with SARS-CoV-2 viral entry into cells. We also describe evidence on the effect of several vitamins, phytochemicals, and naturally occurring compounds on ACE2 expression and activity in various tissues and disease models. This comprehensive review aims to provide a timely compendium on the potential impact of commonly prescribed drugs and pharmacologically active compounds on COVID-19 pathology and risk through regulation of ACE2 and RAS signaling.

Angiotensin-(1-7)-A Potential Remedy for AKI: Insights Derived from the COVID-19 Pandemic

Membrane-bound angiotensin converting enzyme (ACE) 2 serves as a receptor for the Sars-CoV-2 spike protein, permitting viral attachment to target host cells. The COVID-19 pandemic brought into light ACE2, its principal product angiotensin (Ang) 1-7, and the G protein-coupled receptor for the heptapeptide (MasR), which together form a still under-recognized arm of the renin–angiotensin system (RAS). This axis counteracts vasoconstriction, inflammation and fibrosis, generated by the more familiar deleterious arm of RAS, including ACE, Ang II and the ang II type 1 receptor (AT1R). The COVID-19 disease is characterized by the depletion of ACE2 and Ang-(1-7), conceivably playing a central role in the devastating cytokine storm that characterizes this disorder. ACE2 repletion and the administration of Ang-(1-7) constitute the therapeutic options currently tested in the management of severe COVID-19 disease cases. Based on their beneficial effects, both ACE2 and Ang-(1-7) have also been suggested to slow the progression of experimental diabetic and hypertensive chronic kidney disease (CKD). Herein, we report a further step undertaken recently, utilizing this type of intervention in the management of evolving acute kidney injury (AKI), with the expectation of renal vasodilation and the attenuation of oxidative stress, inflammation, renal parenchymal damage and subsequent fibrosis. Most outcomes indicate that triggering the ACE2/Ang-(1-7)/MasR axis may be renoprotective in the setup of AKI. Yet, there is contradicting evidence that under certain conditions it may accelerate renal damage in CKD and AKI. The nature of these conflicting outcomes requires further elucidation.

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.

Angiotensin-converting enzyme 2 and kidney diseases in the era of coronavirus disease 2019

In the decades since the discovery of angiotensin-converting enzyme 2 (ACE2), its protective role in terms of antagonizing activation of the classical renin-angiotensin system (RAS) axis has been recognized in clinical and experimental studies on kidney and cardiovascular diseases. The effects of ACE inhibitor/angiotensin type 1 receptor blockers (ACEi/ARBs) on ACE2-angiotensin-(1-7) (Ang- (1-7))-Mas receptor (MasR) axis activation has encouraged the use of such blockers in patients with kidney and cardiovascular diseases, until the emergence of coronavirus disease 2019 (COVID-19). The previously unchallenged functions of the ACE2-Ang-(1-7)-MasR axis and ACEi/ARBs are being re-evaluated in the era of COVID-19; the hypothesis is that ACEi/ARBs may increase the risk of severe acute respiratory syndrome coronavirus 2 infection by upregulating the human ACE2 receptor expression level. In this review, we examine ACE2 molecular structure, function (as an enzyme of the RAS), and distribution. We explore the roles played by ACE2 in kidney, cardiovascular, and pulmonary diseases, highlighting studies that defined the benefits imparted when ACEi/ARBs activated the local ACE2- Ang-(1-7)-MasR axis. Finally, the question of whether ACEi/ARBs therapies should be stopped in COVID-19-infected patients will be reviewed by reference to the available evidence.

Renin-angiotensin system blockade in the COVID-19 pandemic

In the early months of the coronavirus disease 2019 (COVID-19) pandemic, a hypothesis emerged suggesting that pharmacologic inhibitors of the renin–angiotensin system (RAS) may increase COVID-19 severity. This hypothesis was based on the role of angiotensin-converting enzyme 2 (ACE2), a counterregulatory component of the RAS, as the binding site for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), allowing viral entry into host cells. Extrapolations from prior evidence led to speculation that upregulation of ACE2 by RAS blockade may increase the risk of adverse outcomes from COVID-19. However, counterarguments pointed to evidence of potential protective effects of ACE2 and RAS blockade with regard to acute lung injury, as well as substantial risks from discontinuing these commonly used and important medications. Here we provide an overview of classic RAS physiology and the crucial role of ACE2 in systemic pathways affected by COVID-19. Additionally, we critically review the physiologic and epidemiologic evidence surrounding the interactions between RAS blockade and COVID-19. We review recently published trial evidence and propose important future directions to improve upon our understanding of these relationships.

Double trouble: combined cardiovascular effects of particulate matter exposure and coronavirus disease 2019

The coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has rapidly grown into a pandemic. According to initial reports, the lungs were thought to be the primary target, but recent case studies have shown its reach can extend to other organs including the heart and blood vessels. The severity of cardiac complications of COVID-19 depends on multiple underlying factors, with air pollutant exposure being one of them, as reported by several recent studies. Airborne particulate matter (PM) attracts heightened attention due to its implication in various diseases, especially respiratory and cardiovascular diseases. Inhaled PM not only carries microorganisms inside the body but also elicits local and systemic inflammatory responses resulting in altering the host's immunity and increasing susceptibility to infection. Previous and recent studies have documented that PM acts as a 'carrier' for the virus and aids in spreading viral infections. This review presents the mechanisms and effects of viral entry and how pollution can potentially modulate pathophysiological processes in the heart. We aimed to concisely summarize studies examining cardiovascular outcomes in COVID-19 patients and postulate on how PM can influence these outcomes. We have also reviewed evidence on the use of renin-angiotensin system inhibitors, namely angiotensin-converting enzyme inhibitors and angiotensin receptor blockers, in patients with COVID-19. The interplay of pollution and SARS-CoV-2 is essential to understanding the effects of accentuated cardiovascular effects of COVID-19 and deserves in-depth experimental investigations.

Severe Acute Respiratory Syndrome Coronavirus 2, COVID-19, and the Renin-Angiotensin System: Pressing Needs and Best Research Practices

The coronavirus disease 2019 (COVID-19) pandemic is associated with significant morbidity and mortality throughout the world, predominantly due to lung and cardiovascular injury. The virus responsible for COVID-19-severe acute respiratory syndrome coronavirus 2-gains entry into host cells via ACE2 (angiotensin-converting enzyme 2). ACE2 is a primary enzyme within the key counter-regulatory pathway of the renin-angiotensin system (RAS), which acts to oppose the actions of Ang (angiotensin) II by generating Ang-(1-7) to reduce inflammation and fibrosis and mitigate end organ damage. As COVID-19 spans multiple organ systems linked to the cardiovascular system, it is imperative to understand clearly how severe acute respiratory syndrome coronavirus 2 may affect the multifaceted RAS. In addition, recognition of the role of ACE2 and the RAS in COVID-19 has renewed interest in its role in the pathophysiology of cardiovascular disease in general. We provide researchers with a framework of best practices in basic and clinical research to interrogate the RAS using appropriate methodology, especially those who are relatively new to the field. This is crucial, as there are many limitations inherent in investigating the RAS in experimental models and in humans. We discuss sound methodological approaches to quantifying enzyme content and activity (ACE, ACE2), peptides (Ang II, Ang-[1-7]), and receptors (types 1 and 2 Ang II receptors, Mas receptor). Our goal is to ensure appropriate research methodology for investigations of the RAS in patients with severe acute respiratory syndrome coronavirus 2 and COVID-19 to ensure optimal rigor and reproducibility and appropriate interpretation of results from these investigations.

Severe acute respiratory syndrome coronavirus 2 and renin-angiotensin system blockers: A review and pooled analysis

A novel coronavirus called severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is causing an international outbreak of respiratory illness described as coronavirus disease 2019 (COVID-19). SARS-CoV-2 infects human cells by binding to angiotensin-converting enzyme 2. Small studies suggest that renin-angiotensin system (RAS) blockers may upregulate the expression of angiotensin-converting enzyme 2, affecting susceptibility to SARS-CoV-2. This may be of great importance considering the large number of patients worldwide who are treated with RAS blockers, and the well-proven clinical benefit of these treatments in several cardiovascular conditions. In contrast, RAS blockers have also been associated with better outcomes in pneumonia models, and may be beneficial in COVID-19. This review sought to analyse the evidence regarding RAS blockers in the context of COVID-19 and to perform a pooled analysis of the published observational studies to guide clinical decision making. A total of 21 studies were included, comprising 11,539 patients, of whom 3417 (29.6%) were treated with RAS blockers. All-cause mortality occurred in 587/3417 (17.1%) patients with RAS blocker treatment and in 982/8122 (12.1%) patients without RAS blocker treatment (odds ratio 1.00, 95% confidence interval 0.69-1.45; P=0.49; I²=84%). As several hypotheses can be drawn from experimental analysis, we also present the ongoing randomized studies assessing the efficacy and safety of RAS blockers in patients with COVID-19. In conclusion, according to the current data and the results of the pooled analysis, there is no evidence supporting any harmful effect of RAS blockers on the course of patients with COVID-19, and it seems reasonable to recommend their continuation.

Dysregulation of Angiotensin Converting Enzyme 2 Expression and Function in Comorbid Disease Conditions Possibly Contributes to Coronavirus Infectious Disease 2019 Complication Severity

ACE2 has emerged as a double agent in the COVID-19 ordeal, as it is both physiologically protective and virally conducive. The identification of ACE2 in as many as 72 tissues suggests that extrapulmonary invasion and damage is likely, which indeed has already been demonstrated by cardiovascular and gastrointestinal symptoms. On the other hand, identifying ACE2 dysregulation in patients with comorbidities may offer insight as to why COVID-19 symptoms are often more severe in these individuals. This may be attributed to a pre-existing proinflammatory state that is further propelled with the cytokine storm induced by SARS-CoV-2 infection or the loss of functional ACE2 expression as a result of viral internalization. Here, we aim to characterize the distribution and role of ACE2 in various organs to highlight the scope of damage that may arise upon SARS-CoV-2 invasion. Furthermore, by examining the disruption of ACE2 in several comorbid diseases, we offer insight into potential causes of increased severity of COVID-19 symptoms in certain individuals. SIGNIFICANCE STATEMENT: Cell surface expression of ACE2 determines the tissue susceptibility for coronavirus infectious disease 2019 infection. Comorbid disease conditions altering ACE2 expression could increase the patient's vulnerability for the disease and its complications, either directly, through modulation of viral infection, or indirectly, through alteration of inflammatory status.

Plasma ACE2 and risk of death or cardiometabolic diseases: a case-cohort analysis

BACKGROUND

Angiotensin-converting enzyme 2 (ACE2) is an endogenous counter-regulator of the renin-angiotensin hormonal cascade. We assessed whether plasma ACE2 concentrations were associated with greater risk of death or cardiovascular disease events.

METHODS

We used data from the Prospective Urban Rural Epidemiology (PURE) prospective study to conduct a case-cohort analysis within a subset of PURE participants (from 14 countries across five continents: Africa, Asia, Europe, North America, and South America). We measured plasma concentrations of ACE2 and assessed potential determinants of plasma ACE2 levels as well as the association of ACE2 with cardiovascular events.

FINDINGS

We included 10 753 PURE participants in our study. Increased concentration of plasma ACE2 was associated with increased risk of total deaths (hazard ratio [HR] 1·35 per 1 SD increase [95% CI 1·29-1·43]) with similar increases in cardiovascular and non-cardiovascular deaths. Plasma ACE2 concentration was also associated with higher risk of incident heart failure (HR 1·27 per 1 SD increase [1·10-1·46]), myocardial infarction (HR 1·23 per 1 SD increase [1·13-1·33]), stroke (HR 1·21 per 1 SD increase [1·10-1·32]) and diabetes (HR 1·44 per 1 SD increase [1·36-1·52]). These findings were independent of age, sex, ancestry, and traditional cardiac risk factors. With the exception of incident heart failure events, the independent relationship of ACE2 with the clinical endpoints, including death, remained robust after adjustment for BNP. The highest-ranked determinants of ACE2 concentrations were sex, geographic ancestry, and body-mass index (BMI). When compared with clinical risk factors (smoking, diabetes, blood pressure, lipids, and BMI), ACE2 was the highest ranked predictor of death, and superseded several risk factors as a predictor of heart failure, stroke, and myocardial infarction.

INTERPRETATION

Increased plasma ACE2 concentration was associated with increased risk of major cardiovascular events in a global study.

FUNDING

Canadian Institute of Health Research, Heart & Stroke Foundation of Canada, and Bayer.

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.

The Yin and Yang of ACE/ACE2 Pathways: The Rationale for the Use of Renin-Angiotensin System Inhibitors in COVID-19 Patients

The article describes the rationale for inhibition of the renin-angiotensin system (RAS) pathways as specific targets in patients infected by SARS-CoV-2 in order to prevent positive feedback-loop mechanisms. Based purely on experimental studies in which RAS pathway inhibitors were administered in vivo to humans/rodents, a reasonable hypothesis of using inhibitors that block both ACE and ACE2 zinc metalloproteases and their downstream pathways in COVID-19 patients will be proposed. In particular, metal (zinc) chelators and renin inhibitors may work alone or in combination to inhibit the positive feedback loops (initially triggered by SARS-CoV-2 and subsequently sustained by hypoxia independently on viral trigger) as both arms of renin-angiotensin system are upregulated, leading to critical, advanced and untreatable stages of the disease.

SARS-CoV-2 and diabetes: New challenges for the disease

A novel small enveloped RNA virus with the typical characteristic of the family to which it belongs, a crown, hence the name coronavirus, appeared in December 2019 in Wuhan, China, and subdued the world to its influence. The particular severity of the disease and higher mortality rates in patients with associated morbidities, including hypertension, obesity and diabetes, increases the concern over the consequences of this pandemic. In this review, the features of SARS-CoV-2 will be addressed, as well as the reasons why it poses a particular challenge to diabetic patients. We will also highlight the recent treatment strategies being explored to control this pandemic. Emerging evidence demonstrates that the correct management of diabetes in those patients infected with SARS-CoV-2 is of utmost importance for the viral disease progression, therefore, the importance of blood glucose control will also be addressed.

Critical Role of Neprilysin in Kidney Angiotensin Metabolism

RATIONALE

Kidney homeostasis is critically determined by the coordinated activity of the renin-angiotensin system (RAS), including the balanced synthesis of its main effector peptides Ang (angiotensin) II and Ang (1-7). The condition of enzymatic overproduction of Ang II relative to Ang (1-7) is termed RAS dysregulation and leads to cellular signals, which promote hypertension and organ damage, and ultimately progressive kidney failure. ACE2 (angiotensin-converting enzyme 2) and NEP (neprilysin) induce the alternative, and potentially reno-protective axis by enhancing Ang (1-7) production. However, their individual contribution to baseline RAS balance and whether their activities change in chronic kidney disease (CKD) has not yet been elucidated.

OBJECTIVE

To examine whether NEP-mediated Ang (1-7) generation exceeds Ang II formation in the healthy kidney compared with diseased kidney.

METHODS AND RESULTS

In this exploratory study, we used liquid chromatography-tandem mass spectrometry to measure Ang II and Ang (1-7) synthesis rates of ACE, chymase and NEP, ACE2, PEP (prolyl-endopeptidase), PCP (prolyl-carboxypeptidase) in kidney biopsy homogenates in 11 healthy living kidney donors, and 12 patients with CKD. The spatial expression of RAS enzymes was determined by immunohistochemistry. Healthy kidneys showed higher NEP-mediated Ang (1-7) synthesis than Ang II formation, thus displaying a strong preference towards the reno-protective alternative RAS axis. In contrast, in CKD kidneys higher levels of Ang II were recorded, which originated from mast cell chymase activity.

CONCLUSIONS

Ang (1-7) is the dominant RAS peptide in healthy human kidneys with NEP rather than ACE2 being essential for its generation. Severe RAS dysregulation is present in CKD dictated by high chymase-mediated Ang II formation. Kidney RAS enzyme analysis might lead to novel therapeutic approaches for CKD.

Mesenchymal stem cells modified with angiotensin-converting enzyme 2 are superior for amelioration of glomerular fibrosis in diabetic nephropathy

AIMS

This study aimed to detect the effect of angiotensin-converting enzyme (ACE) 2-modified mesenchymal stem cells (MSCs) on glomerular fibrosis in vitro and in vivo and investigate the underlying molecular mechanism.

METHODS

MSCs transduced with the ACE2 gene (MSCs-ACE2) were cocultured with glomerular mesangial cells (GMCs) following Ang II stimulation. MSCs-ACE2 were transplanted into streptozotocin-induced diabetic rats. Physical, biochemical and morphological parameters were measured, and fibrotic indicators and renin-angiotensin system (RAS) components in GMCs and kidney tissues were assessed.

RESULTS

The transduction efficiency of MSCs was as high as 85%. The modified MSCs secreted soluble ACE2 protein into the culture medium. After transplantation into rats with diabetes, MSCs-ACE2 targeted injured kidneys and enhanced local expression of ACE2. Compared with MSC treatment alone, MSC-ACE2 treatment was superior in reducing albuminuria and improving glomerulosclerosis. In vitro and in vivo, MSCs-ACE2 were more beneficial than MSCs alone in decreasing Ang II and increasing Ang1-7, thereby inhibiting the detrimental effects of Ang II accumulation by downregulating collagen I and fibronectin (FN) expression and inhibiting the transforming growth factor (TGF-β)/Smad pathway.

CONCLUSIONS

MSCs modified with ACE2 therapy have additional benefits to the progression of diabetic nephropathy (DN) by inhibiting renal RAS activation and reducing glomerular fibrosis.

OIP5-AS1 Attenuates Microangiopathy in Diabetic Mouse by Regulating miR-200b/ACE2

OBJECTIVE

This study aimed to investigate OIP5-AS1 effects on microangiopathy in diabetic mouse.

METHODS

The expression levels of OIP5-AS1, miR-200b, and ACE2 expression were measured by RT-qPCR. Western blot was conducted to detect The ACE2 and Ang-(1-7) expression. Luciferase reporter assays were used to identify the interaction between miR-200b and OIP5-AS1 or ACE2. Morris water maze test was performed for detecting cognitive function.

RESULTS

Our results indicated that diabetic mice exhibited much lower OIP5-AS1 expression in the hippocampus than normal mice. Diabetic mice of OIP5-AS1 KO group showed remarkably lower OIP5-AS1 expression in the hippocampus, longer escape latency and lower percentage of CD31+ cells in the hippocampusthan those of WT group. OIP5-AS1 knockdown directly up-regulated miR-200b expression and ACE2 was directly inhibited by miR-200b. Relative to normal mice, diabetic mice had markedly higher miR-200b expression and lower ACE2 expression in the hippocampus. Diabetic mice of OIP5-AS1 KO group were with obviously higher miR-200b expression and lower ACE2 expression in the hippocampus than those of WT group. Compared with diabetic mice of OIP5-AS1 KO group, those of WT group, OIP5-AS1 KO + miR-200b inhibitor group and OIP5-AS1 KO + ACE2 group had obviously shorter escape latency and higher percentage of CD31⁺ cells and more caspase-3 protein expression in the hippocampus.

CONCLUSIONS

OIP5-AS1 attenuated microangiopathy in diabetic mouse by regulating miR-200b/ACE2.

Development and validation of an LC-MS/MS method for detection and quantification of in vivo derived metabolites of [Pyr1]apelin-13 in humans

[Pyr1]apelin-13 is the predominant apelin peptide isoform in the human cardiovascular system and plasma. To date, few studies have investigated [Pyr1]apelin-13 metabolism in vivo in rats with no studies examining its stability in humans. We therefore aimed to develop an LC-MS/MS method for detection and quantification of intact [Pyr1]apelin-13 and have used this method to identify the metabolites generated in vivo in humans. [Pyr1]apelin-13 (135 nmol/min) was infused into six healthy human volunteers for 120 minutes and blood collected at time 0 and 120 minutes after infusion. Plasma was extracted in the presence of guanidine hydrochloride and analysed by LC-MS/MS. Here we report a highly sensitive, robust and reproducible method for quantification of intact [Pyr1]apelin-13 and its metabolites in human plasma. Using this method, we showed that the circulating concentration of intact peptide was 58.3 ± 10.5 ng/ml after 120 minutes infusion. We demonstrated for the first time that in humans, [Pyr1]apelin-13 was cleaved from both termini but the C-terminal was more susceptible to cleavage. Consequently, of the metabolites identified, [Pyr1]apelin-13(1-12), [Pyr1]apelin-13(1-10) and [Pyr1]apelin-13(1-6) were the most abundant. These data suggest that apelin peptides designed for use as cardiovascular therapeutics, should include modifications that minimise C-terminal cleavage.

Aliskiren Attenuates the Inflammatory Response and Wound Healing Process in Diabetic Mice With Periodontal Disease

The aim of this study was to characterize the role of local RAS (renin–angiotensin system) in the inflammatory response of normal (N) and diabetic (D) mice with periodontal disease (PD). Diabetes Mellitus (DM) was induced by peritoneal injection of streptozotocin in Balb/c mice. PD was induced by ligature around the first molar in both N and D, irrespective of whether they were treated with aliskiren (50 mg/kg, Alisk). Mandibles were harvested for histomorphometric analyses, and gingival tissue (GT) was collected to evaluate gene expression and extracellular matrix components (ECM). Immunohistochemical (IHC) analyses were used to localize RAS in GT. The production of C-reactive protein (CRP), IL-1β, CXCL2, and CCL8 was evaluated by enzyme-linked immunosorbent assay (ELISA). Renin was found to exacerbate the inflammation and periodontal bone loss at 14 days after PD, and Alisk inhibited this process in GT of N and D. PD increased CRP, CXCL2, CCL8, and IL-1β production in both animals. Alisk could inhibit CRP, CXCL2, and CCL8 primarily in D animals. However, only CCL8 was decreased in N animals after Alisk pretreatment. PD enhanced expression and production of AGT, ACE, AT1R, and AT2R in both N and D. AT1R expression was higher in D with PD, and AT2R expression was higher in N with PD. ACE2 and receptor Mas (MasR) expression and production was elevated in the control group of both animals. PD inhibited ACE2 in N but not in D. MasR expression was unaffected in both N and D with PD. Alisk reduced expression and production of all RAS components in GT of both animals, except for ACE2 in N. RAS staining was observed in all layers of epithelium, basal cell layer, and lamina propria and was higher in N with PD. Col1a1, Col1a2, Col3a1, and fibronectin (Fn1) were increased in both animals with PD. Alisk inhibited Col1a1 and Fn in both animals, Col1a2 was decreased only in D, while levels of Col3a1 remained unchanged in all animal groups. In conclusion, these data demonstrated the presence and functional role of local RAS in GT, exacerbating the inflammatory response, periodontal bone loss, and wound healing processes in both N and D animal groups. In addition, Alisk was able to significantly reduce gingival inflammation, excessive wound healing processes, and periodontal bone loss.

Absence of the β1 subunit of AMP-activated protein kinase reduces myofibroblast infiltration of the kidneys in early diabetes

Activation of the heterotrimeric energy-sensing kinase AMP-activated protein kinase (AMPK) has been reported to improve experimental diabetic kidney disease. We examined the effect of type 1 diabetes in wild-type (WT) mice and mice lacking the β1 subunit of AMPK (AMPK β1^-/- mice), which have reduced AMPK activity in kidneys and other organs. Diabetes was induced using streptozotocin (STZ) and the animals followed up for 4 weeks. Hyperglycaemia was more severe in diabetic AMPK β1^-/- mice, despite the absence of any difference in serum levels of insulin, adiponectin and leptin. There was no change in AMPK activity in the kidneys of diabetic WT mice by AMPK activity assay, or phosphorylation of either the αT172 activation site on the α catalytic subunit of AMPK or the AMPK-specific phosphosite S79 on acetyl CoA carboxylase 1 (ACC1). Phosphorylation of the inhibitory αS485 site on the α subunit of AMPK was significantly increased in the WT diabetic mice compared to non-diabetic controls. Despite increased plasma glucose levels in the diabetic AMPK β1^-/- mice, there were fewer myofibroblasts in the kidneys compared to diabetic WT mice, as evidenced by reduced α-smooth muscle actin (α-SMA) protein by Western blot, mRNA by qRT-PCR and fewer α-SMA-positive cells by immunohistochemical staining. Albuminuria was also reduced in the AMPK β1^-/- mice. In contrast to previous studies, therefore, myofibroblasts were reduced in the kidneys of AMPK β1^-/- diabetic mice compared to diabetic WT mice, despite increased circulating glucose, suggesting that AMPK can worsen renal fibrosis in type 1 diabetes.

Cardiovascular Disease and Diabetic Kidney Disease

Diabetic kidney disease commonly is associated with an increased risk of cardiovascular disease. There are traditional common risk factors for both conditions including hypertension and poor glycemic control. However, it is likely that there are other pathophysiological mechanisms that explain the clinical phenomenon of increased cardiovascular disease in diabetic patients with chronic kidney and vice versa. Current management of both conditions includes aggressive glucose and blood pressure control. The protective role of treating dyslipidemia has been shown for cardiovascular disease, but the results for renal disease are not as clear. The advent of new classes of glucose-lowering agents such as sodium glucose co-transporter2 inhibitors and glucagon-like peptide-1 agonists has resulted in impressive effects on both cardiovascular and renal disease in diabetes. However, how these drugs act independently of glucose lowering to confer both kidney and cardiovascular protection has not been fully elucidated. Nevertheless, these new treatments provide optimism for reducing both microvascular and macrovascular complications in diabetes, which represent the major causes of morbidity and premature mortality in this condition.

Fetal programming and the angiotensin-(1-7) axis: a review of the experimental and clinical data

Hypertension is the primary risk factor for cardiovascular disease that constitutes a serious worldwide health concern and a significant healthcare burden. As the majority of hypertension has an unknown etiology, considerable research efforts in both experimental models and human cohorts has focused on the premise that alterations in the fetal and perinatal environment are key factors in the development of hypertension in children and adults. The exact mechanisms of how fetal programming events increase the risk of hypertension and cardiovascular disease are not fully elaborated; however, the focus on alterations in the biochemical components and functional aspects of the renin-angiotensin (Ang) system (RAS) has predominated, particularly activation of the Ang-converting enzyme (ACE)-Ang II-Ang type 1 receptor (AT1R) axis. The emerging view of alternative pathways within the RAS that may functionally antagonize the Ang II axis raise the possibility that programming events also target the non-classical components of the RAS as an additional mechanism contributing to the development and progression of hypertension. In the current review, we evaluate the potential role of the ACE2-Ang-(1-7)-Mas receptor (MasR) axis of the RAS in fetal programming events and cardiovascular and renal dysfunction. Specifically, the review examines the impact of fetal programming on the Ang-(1-7) axis within the circulation, kidney, and brain such that the loss of Ang-(1-7) expression or tone, contributes to the chronic dysregulation of blood pressure (BP) and cardiometabolic disease in the offspring, as well as the influence of sex on potential programming of this pathway.

Loss of Apelin Augments Angiotensin II-Induced Cardiac Dysfunction and Pathological Remodeling

Apelin is an inotropic and cardioprotective peptide that exhibits beneficial effects through activation of the APJ receptor in the pathology of cardiovascular diseases. Apelin induces the expression of angiotensin-converting enzyme 2 (ACE2) in failing hearts, thereby improving heart function in an angiotensin 1⁻7-dependent manner. Whether apelin antagonizes the over-activation of the renin⁻angiotensin system in the heart remains elusive. In this study we show that the detrimental effects of angiotensin II (Ang II) were exacerbated in the hearts of aged apelin-gene-deficient mice. Ang II-mediated cardiac dysfunction and hypertrophy were augmented in apelin knockout mice. The loss of apelin increased the ratio of angiotensin-converting enzyme (ACE) to ACE2 expression in the Ang II-stressed hearts, and Ang II-induced cardiac fibrosis was markedly enhanced in apelin knockout mice. mRNA expression of pro-fibrotic genes, such as transforming growth-factor beta (TGF-β) signaling, were significantly upregulated in apelin knockout hearts. Consistently, treatment with the ACE-inhibitor Captopril decreased cardiac contractility in apelin knockout mice. In vitro, apelin ameliorated Ang II-induced TGF-β expression in primary cardiomyocytes, accompanied with reduced hypertrophy. These results provide direct evidence that endogenous apelin plays a crucial role in suppressing Ang II-induced cardiac dysfunction and pathological remodeling.

Egg White-Derived Tripeptide IRW (Ile-Arg-Trp) Is an Activator of Angiotensin Converting Enzyme 2

Angiotensin converting enzyme 2 (ACE2) plays beneficial roles in the renin angiotensin aldosterone system. Our previous studies indicated that egg white-derived antihypertensive peptide IRW (Ile-Arg-Trp) could upregulate ACE2 mRNA level in mesenteric artery of spontaneously hypertensive rats (SHRs), suggesting the potential of IRW as an in vivo ACE2 activator. In this study, the effects of IRW on activity and protein expression of ACE2 were investigated. Results indicated that IRW activated human recombinant ACE2 with an EC₅₀ value of 7.24 × 10^-5 M. In rat aortic vascular smooth muscle cell line A7r5 cells, IRW treatment (50 μM) significantly increased the expression and activity of ACE2. Oral administration of IRW to SHRs upregulated ACE2 protein levels in kidney and aorta. Molecular docking study suggested that IRW might activate ACE2 through interaction with the subdomain I near the active site through hydrogen bonds. Overall, this study established IRW as the first food-derived ACE2 activating peptide.

Sex dimorphism in ANGII-mediated crosstalk between ACE2 and ACE in diabetic nephropathy

Angiotensin-converting enzyme (ACE) and ACE2 play a critical role in the renin-angiotensin system (RAS) by altering angiotensin II (ANGII) levels, thus governing its deleterious effects. Both enzymes are altered by sex and diabetes, and play an important role in the development of diabetic nephropathy (DN). Importantly, previous evidence in diabetic and ACE2-deficient (ACE2KO) males suggest a sex-dependent crosstalk between renal ACE and ACE2. In the present work, we aimed to study the sex-specific susceptibility to diabetes and direct infusion of ANGII in kidney disease progression, with a special focus on its link to ACE2 and ACE. In our mouse model, ANGII promoted hypertension, albuminuria, reduced glomerular filtration, and glomerular histological alterations. ANGII adverse effects were accentuated by diabetes and ACE2 deficiency, in a sex-dependent fashion: ACE2 deficiency accentuated ANGII-induced hypertension, albuminuria, and glomerular hypertrophy in diabetic females, whereas in diabetic males exacerbated ANGII-mediated glomerular hypertrophy, mesangial expansion, and podocyte loss. At the molecular level, ANGII downregulated renal ACE gene and enzymatic activity levels, as well as renin gene expression in ACE2KO mice. Interestingly, male sex and diabetes accentuated this effect. Here we show sex dimorphism in the severity of diabetes- and ANGII-related renal lesions, and demonstrate that ACE2- and ACE-related compensatory mechanisms are sex-specific. Supporting our previous findings, the modulation and ANGII-mediated crosstalk between ACE2 and ACE in DN progression was more evident in males. This work increases the understanding of the sex-specific role of ACE2 and ACE in DN, reinforcing the necessity of more personalized treatments targeting RAS.

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.

Intestinal dysbiosis activates renal renin-angiotensin system contributing to incipient diabetic nephropathy

Considerable interest nowadays has focused on gut microbiota owing to their pleiotropic roles in human health and diseases. This intestinal community can arouse a variety of activities in the host and function as "a microbial organ" by generating bioactive metabolites and participating in a series of metabolism-dependent pathways. Alternations in the composition of gut microbiota, referred to as intestinal dysbiosis, are reportedly associated with several diseases, especially diabetes mellitus and its complications. Here we focus on the relationship between gut microbiota and diabetic nephropathy (DN), as the latter is one of the major causes of chronic kidney diseases. The activation of renin angiotensin system (RAS) is a critical factor to the onset of DN, and emerging data has demonstrated a provoking and mediating role of gut microbiota for this system in the context of metabolic diseases. The purpose of the current review is to highlight some research updates about the underlying interplay between gut microbiota, their metabolites, and the development and progression of DN, along with exploring innovative approaches to targeting this intestinal community as a therapeutic perspective in clinical management of DN patients.