Serum Angiotensin-converting Enzyme 2 Research Articles

Is there any relationship between serum zinc levels and angiotensin-converting enzyme 2 gene expression in patients with coronavirus disease 2019?

BackgroundThe level of angiotensin-converting enzyme 2 (ACE2) expression in different tissues is essential in the sensitivity, symptoms and consequences of COVID-19 infection. It seems that zinc is involved in the structure of the ACE2 enzyme has been identified; nonetheless, the relationship between ACE2 expression and zinc serum levels in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected patients is still unclear. This study aimed to evaluate the expression of ACE2 in peripheral blood-derived immune cells of COVID-19 patients and its relationship with serum zinc levels. MethodsThirty healthy subjects and thirty patients with COVID-19 were enrolled in this study. The COVID-19 infection was confirmed by positive real-time polymerase chain reaction (RT-PCR) and radiological data. Peripheral blood samples were taken from healthy subjects and COVID-19 patients. Whole blood samples were also used to measure ACE2 gene expression by RT-PCR technique. The correlation matrix evaluated the relationship between ACE2 expression, serum zinc levels, and other related variables. ResultsThe outcomes showed no considerable alteration in serum zinc levels between patients and the control group. Likewise, the ACE2 gene expression results showed a significant decrease in this receptor's expression in COVID-19 patients compared with the healthy subjects. A significant positive correlation was observed between serum zinc level and ACE2 gene expression in patients with COVID-19. ConclusionThe immune system seems to reduce the mRNA expression of the ACE2 in the peripheral blood leukocytes following SARS-CoV-2 infection. Moreover, zinc deficiency can make patients more susceptible to SARS-CoV-2 infection.

Changes in the SARS-CoV-2 cellular receptor ACE2 levels in cardiovascular patients: a potential biomarker for the stratification of COVID-19 patients

Angiotensin-converting enzyme 2 (ACE2) is essential for SARS-CoV-2 cellular entry. Here we studied the effects of common comorbidities in severe COVID-19 on ACE2 expression. ACE2 levels (by enzyme activity and ELISA measurements) were determined in human serum, heart and lung samples from patients with hypertension (n = 540), heart transplantation (289) and thoracic surgery (n = 49). Healthy individuals (n = 46) represented the controls. Serum ACE2 activity was increased in hypertensive subjects (132%) and substantially elevated in end-stage heart failure patients (689%) and showed a strong negative correlation with the left ventricular ejection fraction. Serum ACE2 activity was higher in male (147%), overweight (122%), obese (126%) and elderly (115%) hypertensive patients. Primary lung cancer resulted in higher circulating ACE2 activity, without affecting ACE2 levels in the surrounding lung tissue. Male sex resulted in elevated serum ACE2 activities in patients with heart transplantation or thoracic surgery (146% and 150%, respectively). Left ventricular (tissular) ACE2 activity was unaffected by sex and was lower in overweight (67%), obese (62%) and older (73%) patients with end-stage heart failure. There was no correlation between serum and tissular (left ventricular or lung) ACE2 activities. Neither serum nor tissue (left ventricle or lung) ACE2 levels were affected by RAS inhibitory medications. Abandoning of ACEi treatment (non-compliance) resulted in elevated blood pressure without effects on circulating ACE2 activities. ACE2 levels associate with the severity of cardiovascular diseases, suggestive for a role of ACE2 in the pathomechanisms of cardiovascular diseases and providing a potential explanation for the higher mortality of COVID-19 among cardiovascular patients. Abandoning RAS inhibitory medication worsens the cardiovascular status without affecting circulating or tissue ACE2 levels.

Lack of Association Between ACE2 Expression and Serum Testosterone Concentrations in Peripheral Mononuclear Cells in Males

Background: Male sex is a risk factor for developing severe COVID-19 illness, hospitalization, and mortality. It is possible that the male sex hormone, testosterone, contributes to the morbidity from COVID-19. SARS-CoV2 viruses use cell membrane protein Angiotensin-Converting Enzyme 2 (ACE2) receptor and undergo S protein priming by the Type II Transmembrane Serine Protease (TMPRSS2) to enter the cells. Hence, the expression level of ACE2 and TMPRSS2 may affect disease susceptibility and possible severity. TMPRSS2 is regulated by the androgen receptor. We, therefore, examined if an association exists between serum testosterone concentrations and ACE2 or TMPRSS2 expression level in men. Methods: We analyzed fasting serum samples and peripheral blood mononuclear cells (MNC) from 42 men. Total and free testosterone and estradiol were measured by liquid chromatography/equilibrium dialysis. Sex hormone binding globulin (SHBG) was measured by chemiluminescence. mRNA was prepared from MNC. Quantitative RT-PCR was conducted using commercially available, pre-designed TaqMan primers and probes targeting ACE2. The ACE2 relative level was calculated after normalization to beta Actin and GAPDH, with lowest ACE2 level being set to 1. Results: Subjects’ age ranged from 20 to 65 years. Type 2 diabetes was present in 74% of the men and the mean HbA1 was 7.2±1.6% (mean ± S.D.). Fifteen subjects had subnormal free testosterone (<50 pg/ml). Compared to the 27 subjects with normal free testosterone, they were older (49±12 vs 40±13 years, p=0.03) but had similar BMI (36±10, 35±10 kg/m2, p=0.71). As expected, they had lower total testosterone (Median [25th, 75th percentile]; 222 [171-266] vs 431 [335, 618] ng/dl, p<0.001) and free testosterone concentrations (39 [21, 44] vs 72 [59, 92], p<0.001). Total estradiol was also lower in this group (19±1 vs 29±13 pg/ml, p=0.03) but free estradiol (0.44±0.33 vs 0.56±0.34 pg/ml, p=0.44) and SHBG (27 [19, 33] vs 30 [21, 39] nmol/L, p=0.52) were similar. Quantitative PCR data showed there was a large inter-individual variation of ACE2 expression level, up to 15-fold difference. Average ACE2 level did not differ between subnormal and normal testosterone groups (3.4 [2.7, 5.0] vs 3.9 [2.5, 5.7] arbitrary units). ACE2 expression was not related to free testosterone (r=0.11), free estradiol (r=0.18) or sex hormone binding globulin (r=0.15) on linear regression analyses (p>0.30 for all). ACE2 expression was also not related to age (r= -0.15, p=0.34), BMI (r= -0.2, p=0.23) or presence of diabetes. We were not able to detect a significant expression of TMPRSS2 in MNC. Conclusion: Our results do not support a role for testosterone or estradiol as regulators of ACE2 expression in peripheral blood MNC in males.

Effects of Pennyroyal (Mentha pulegium L.) on Angiotensin Converting Enzyme-2 (ACE-2) and Antioxidant Parameters in Rabbits

Many studies have been conducted on medicinal aromatic plants in recent years. Alternative medicine particularly comes to the fore as an alternative to the use of synthetic agents. The antioxidant, anti-inflammatory, antimicrobial and antiviral effects of phenolic compounds, especially in the structure of aromatic plants, are known. Among those well-known aromatic plants, Pennyroyal (Mentha pulegium L.) is known to contain a large amount of phenolic compounds. In our study, by taking these effects of phenolic compounds into consideration, the effectiveness of pennyroyal on antioxidant parameters and Angiotensin-converting enzyme 2 (ACE2) which is the receptor that Covid-19 binds, and that has many important functions in the organism, was evaluated. A total of 15 New Zealand rabbits were used in the study. The animals were divided into three experimental groups with 5 rabbits in each group. While no Pennyroyal was added to the control group, 0.1% and 0.2% were added to the diets for the other groups. All groups were fed ad-libitum. On the 14th day of the experiment, serum ACE2, GSH and MDA levels were determined with blood taken from the ears of the rabbits. According to the analysis results, while a decrease in ACE2 and MDA levels was determined in the groups which were given 0.1% and 0.2% Pennyroyal compared to the control group, a significant increase was observed in the GSH level. As a result, determining the antioxidant effect of Pennyroyal as well as the effect of decreasing the serum ACE2 level revealed the need for more research to fully explain the effectiveness of aromatic plants in combating Covid-19.

Level of the SARS-CoV-2 receptor ACE2 activity is highly elevated in old-aged patients with aortic stenosis: implications for ACE2 as a biomarker for the severity of COVID-19

Coronavirus disease 2019 (COVID-19) has a high mortality in elderly patients with pre-existing cardiovascular diseases. The cellular receptor of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the angiotensin-converting enzyme 2 (ACE2), thereby implicating a link between cardiovascular diseases and SARS-CoV-2 susceptibility. Aortic stenosis (AS) represents a chronic inflammatory state with severe cardiovascular complications in the elderly, a prime condition for COVID-19 mortality. The circulating ACE2 levels were measured in 111 patients with severe AS and compared to patients with hypertension and healthy individuals. About 4 times higher circulating ACE2 activity was found in patients with severe AS than in hypertensives or healthy individuals (88.3 ± 61.6., n = 111, 20.6 ± 13.4, n = 540, and 16.1 ± 7.4 mU/L, n = 46, respectively). Patients with severe AS were older than patients with hypertension (80 ± 6 years vs. 60 ± 15 years, P < 0.05). Serum ACE2 activity correlated negatively with the left ventricular ejection fraction, aortic root area, TAPSE, and positively with the right ventricular systolic pressure, cardiac diameters in patients with AS. In contrast, circulating ACE2 activity was independent of the blood pressure, peak flow velocity at the aortic root, kidney function (GFR), and inflammatory state (CRP). We found no effect of RAAS inhibitory drugs on the serum ACE2 activity in this group of patients. Our results illustrate circulating ACE2 as a potential interface between chronic inflammation, cardiovascular disease, and COVID-19 susceptibility. Elderly patients with AS have markedly elevated ACE2 levels together with altered left and right ventricular functions, which may pose higher risks during COVID-19. Our clinical data do not support a role for RAAS inhibitors in regulating circulating ACE2 levels.

Decreased serum ACE2 levels in patients with connective tissue diseases.

To evaluate serum concentration and activity of angiotensin-converting enzyme 2 (ACE2) in patients with connective tissue diseases (CTDs). Serum samples from healthy subjects and patients with SLE, systemic sclerosis (SSc), primary Sjögren's syndrome (SS) and RA were collected. The concentration and activity of ACE2 were measured by ELISA and fluorometric method, respectively, and analysed for associations with clinical features and concurrent medications. In total, 66 SLE, 55 SSc, 31 SS and 31 RA patients were involved. ACE2 concentration was significantly decreased in patients with either of the four CTDs compared with healthy subjects. The concentration was not linked to special clinical features expect that it was slightly lower in patients with lupus nephritis than those without. In SLE patients, ACE2 concentration elevated with the increase of glucocorticoids, and was not associated with other treatments. Different from the concentration, ACE2 activity was increased in CTD patients. A weak correlation of ACE2 activity with SLE disease activity index score was also observed. The clinical significance of ACE2 concentration and activity looks quite different among CTD patients. Preliminary data suggest ACE2 levels are not affected by most of the treatments.

Hypothesis: Sex-Related Differences in ACE2 Activity May Contribute to Higher Mortality in Men Versus Women With COVID-19.

Angiotensin-converting enzyme 2 (ACE2) facilitates the cellular entry of the severe acute respiratory syndrome-associated coronavirus 2 (SARS-CoV-2), which causes the coronavirus-2019 (COVID-19) disease. Recent reports have shown worse outcomes in men with COVID-19 infection compared to women. We review the hypothesis that sex-related differences in outcomes in COVID-19 are due to different activity of ACE2 between men and women. We also show that studies in humans have demonstrated no significant difference in serum ACE2 levels between healthy men and women. However, men with hypertension and heart failure typically have higher level of serum ACE2 activity compared to women. We hypothesize that the worse outcomes in men with COVID-19 compared to women is likely due to higher prevalence of hypertension and heart failure among men compared to women. To test this hypothesis, studies to compare the outcomes of COVID-19 infection between men and women with no preexisting heart diseases are needed.

The serum angiotensin-converting enzyme 2 and angiotensin-(1-7) concentrations after optimal therapy for acute decompensated heart failure with reduced ejection fraction.

Objective: Elucidation of the role of angiotensin-converting enzyme (ACE) 2 (ACE2)/angiotensin (Ang)-(1-7)/Mas receptor axis in heart failure is necessary. No previous study has reported serial changes in ACE2 and Ang-(1-7) concentrations after optimal therapy (OT) in acute heart failure (AHF) patients. We aimed to investigate serial changes in serum ACE2 and Ang-(1-7) concentrations after OT in AHF patients with reduced ejection fraction (EF).Methods: ACE2 and Ang-(1-7) concentrations were measured in 68 AHF patients with reduced EF immediately after admission and 1 and 3 months after OT. These parameters were compared with the healthy individuals at three time points.Results: In the acute phase, Ang-(1-7) and ACE2 concentrations was statistically significantly lower and higher in AHF patients than the healthy individuals (2.40 ± 1.11 vs. 3.1 ± 1.1 ng/ml, P<0.005 and 7.45 ± 3.13 vs. 4.84 ± 2.25 ng/ml, P<0.005), respectively. At 1 month after OT, Ang-(1-7) concentration remained lower in AHF patients than the healthy individuals (2.37 ± 1.63 vs. 3.1 ± 1.1 ng/ml, P<0.05); however, there was no statistically significant difference in ACE2 concentration between AHF patients and the healthy individuals. At 3 months after OT, there were no statistically significant differences in Ang-(1-7) and ACE2 concentrations between AHF patients and the healthy individuals.Conclusion: ACE2 concentration was equivalent between AHF patients and the healthy individuals at 1 and 3 months after OT, and Ang-(1-7) concentration was equivalent at 3 months after OT.

P0025BARIATRIC SURGERY MAY REDUCE UPREGULATED EXPRESSION OF FIBROBLAST GROWTH FACTOR 21 AND ANGIOTENSIN-CONVERTING ENZYME 2 IN OBESE PATIENTS

Abstract Background and Aims Recent studies showed that the fibroblast growth factor 21 (FGF21) and angiotensin-converting enzyme 2 (ACE2)/Angiotensin 1-7 (Ang (1-7))/MAS axis of the renin-angiotensin system counteract to the negative role of Ang II in various disease. In this study, we examed FGF21 and ACE2/Ang (1-7) in obesity and its change after bariatric surgery. Method We prospectively enrolled obese patient who performed bariatric surgery and age-sex matched healthy volunteers (HV) (n=12 each). We obtained their clinical information and serum samples. Serum FGF-21, Ang II, ACE2, and Ang (1-7) levels were measured by enzyme-linked immunosorbent assay kits. We measured also FGF-21, Ang II, ACE2, and Ang (1-7) 6 months after bariatric surgery in obese patients (n=12). Results FGF21, Ang II, and ACE2 levels were significantly higher in obese patients compared with HV (p= 0.045, &amp;lt; 0.001, and 0.020, respectively). FGF21, Ang II, and ACE2 levels were significantly decreased after bariatric surgery (p = 0.002, 0.005, and 0.023, respectively). There was no significant difference in Ang (1-7) levels between obese patients and HV (p = 0.887) (Figure 1). Although Ang (1-7) levels did not change after bariatric surgery (p = 0.480), changes in Ang (1-7) levels were positively correlated with changes in body mass index (BMI) (R2 = 0.580, p = 0.048) (Figure 2). Conclusion FGF21 and ACE2 were upregulated in obese patients and they are reduced after bariatric surgery. A decrease in BMI after bariatric surgery could lead to decrease in Ang (1-7).

Association of angiotensin-converting enzyme 2 gene polymorphism and enzymatic activity with essential hypertension in different gender: A case-control study.

Angiotensin-converting enzyme 2 (ACE2) plays an important role in the development of essential hypertension (EH). The aim of this study was to investigate the relationship of ACE2 gene polymorphisms and enzymatic activity with EH in the northeastern Chinese Han population. 34 single-nucleotide polymorphism (SNP) loci of ACE2 were detected in 1024 EH patients and 956 normotensive (NT) controls by Sequenom Mass-ARRAY RS1000. Five SNPs (rs1514283, rs4646155, rs4646176, rs2285666, and rs879922) in ACE2 gene were determined to significantly associate with EH in female participants, while no SNP locus was linked to male group. Specifically, it was the first time to report that rs4646155 was significantly associated with EH in females. Furthermore, the correlation between ACE2 activity and clinical parameters were performed by Pearson correlation analysis in EH patients. We found that the ACE2 activity level was negatively correlated with body mass index (BMI), DBP, and pulse pressure, and significantly positively with ACE2 concentration, blood glucose and estrogen level in female EH patients. These results demonstrated that the genetic variants of ACE2 played vital roles in the development of EH. And the serum ACE2 activity can predict the development of cardiac dysfunction in EH patients.

Impact of angiotensin-converting enzyme 2 levels on postoperative pneumonia after esophagectomy

BackgroundPulmonary complications after esophagectomy are often fatal. The prediction of postoperative pulmonary complications remains a challenge. Accumulating evidence demonstrates a physiological and pathological role for angiotensin-converting enzyme 2 (ACE2) in the respiratory system. The purpose of this study was to evaluate the predictive value of ACE2 levels for the development of postoperative pneumonia. MethodsTo evaluate the association between serum ACE2 levels and pneumonia after esophagectomy, we retrospectively reviewed the medical records of 80 patients who underwent thoracoscopic esophagectomy for esophageal cancer from 2009 to 2014. ResultsNineteen patients (23.8%) developed pneumonia after esophagectomy. Patients with pneumonia had significantly higher levels of ACE2 from the preoperative day to postoperative day (POD) 3, white blood cell count (POD7), and C-reactive protein (POD3, POD5, and POD7) than patients without pneumonia. Patients with postoperative pneumonia had higher serum ACE2 levels on POD3 than patients without pneumonia. ConclusionsThe elevation of ACE2 levels on POD3 may predict the incidence of pneumonia.

Resveratrol Inhibits Growth of Experimental Abdominal Aortic Aneurysm Associated With Upregulation of Angiotensin-Converting Enzyme 2.

Recent evidence suggests an important role for angiotensin-converting enzyme 2 (ACE2) in limiting abdominal aortic aneurysm (AAA). This study examined the effect of ACE2 deficiency on AAA development and the efficacy of resveratrol to upregulate ACE2 in experimental AAA. APPROACH AND RESULTS: Ace2 deletion in apolipoprotein-deficient mice (ApoE-/-Ace2-/y ) resulted in increased aortic diameter and spontaneous aneurysm of the suprarenal aorta associated with increased expression of inflammation and proteolytic enzyme markers. In humans, serum ACE2 activity was negatively associated with AAA diagnosis. ACE2 expression was lower in infrarenal biopsies of patients with AAA than organ donors. AAA was more severe in ApoE-/-Ace2-/y mice compared with controls in 2 experimental models. Resveratrol (0.05/100-g chow) inhibited growth of pre-established AAAs in ApoE-/- mice fed high-fat chow and infused with angiotensin II continuously for 56 days. Reduced suprarenal aorta dilatation in mice receiving resveratrol was associated with elevated serum ACE2 and increased suprarenal aorta tissue levels of ACE2 and sirtuin 1 activity. In addition, the relative phosphorylation of Akt and ERK (extracellular signal-regulated kinase) 1/2 within suprarenal aorta tissue and gene expression for nuclear factor of kappa light polypeptide gene enhancer in B cells 1, angiotensin type-1 receptor, and metallopeptidase 2 and 9 were significantly reduced. Upregulation of ACE2 in human aortic smooth muscle cells by resveratrol in vitro was sirtuin 1-dependent. This study provides experimental evidence of an important role for ACE2 in limiting AAA development and growth. Resveratrol upregulated ACE2 and inhibited AAA growth in a mouse model.

Exercise training modulates the hepatic renin-angiotensin system in fructose-fed rats.

What is the central question of this study? What are the effects of exercise training on the hepatic renin-angiotensin system and their contribution to damage resulting from fructose overload in rats? What is the main finding and its importance? Exercise training attenuated the deleterious actions of the angiotensin-converting enzyme/angiotensinII/angiotensinII type 1 receptor axis and increased expression of the counter-regulatory (angiotensin-converting enzyme 2/angiotensin (1-7)/Mas receptor) axis in the liver. Therefore, our study provides evidence that exercise training modulates the hepatic renin-angiotensin system, which contributes to reducing the progression of metabolic dysfunction and non-alcoholic fatty liver disease in fructose-fed rats. The renin-angiotensin system (RAS) has been implicated in the development of metabolic syndrome. We investigated whether the hepatic RAS is modulated by exercise training and whether this modulation improves the deleterious effects of fructose overload in rats. Male Wistar rats were divided into (n=8 each) control (CT), exercise control (CT-Ex), high-fructose (HFr) and exercise high-fructose (HFr-Ex) groups. Fructose-drinking rats received d-fructose (100gl-1 ). After 2weeks, CT-Ex and HFr-Ex rats were assigned to a treadmill training protocol at moderate intensity for 8weeks (60minday-1 , 4days per week). We assessed body mass, glucose and lipid metabolism, hepatic histopathology, angiotensin-converting enzyme (ACE) and angiotensin-converting enzyme 2 (ACE2) activity, the angiotensin concentration and the expression profile of proteins affecting the hepatic RAS, gluconeogenesis and inflammation. Neither fructose overload nor exercise training influenced body mass gain and serum ACE and ACE2 activity. The HFr group showed hyperinsulinaemia, but exercise training normalized this parameter. Exercise training was effective in preventing hepatic steatosis and in preventing triacylglycerol and glycogen accumulation. Furthermore, exercise improved the response to the deleterious effects of HFr overload by normalizing the gluconeogenesis pathway and the protein levels of interleukin-6 and tumour necrosis factor-α. The HFr rats displayed increased hepatic ACE activity and protein expression and angiotensinII concentration, which were attenuated by exercise training. Exercise training restored the ACE2/angiotensin-(1-7)/Mas receptor axis. Exercise training may favour the counter-regulatory ACE2/angiotensin-(1-7)/Mas receptor axis over the classical RAS (ACE/angiotensin II/angiotensinII type 1 receptor axis), which could be responsible for the reduction of metabolic dysfunction and the prevention of non-alcoholic fatty liver disease.

Angiotensin-converting enzyme 2 amplification limited to the circulation does not protect mice from development of diabetic nephropathy

Blockers of the renin-angiotensin system are effective inthe treatment of experimental and clinical diabetic nephropathy. An approach different from blocking the formation or action of angiotensin II (1-8) that could also be effective involves fostering its degradation. Angiotensin-converting enzyme 2 (ACE2) is a monocarboxypeptidase that cleaves angiotensin II (1-8) to form angiotensin (1-7). Therefore, we examined the renal effects of murine recombinant ACE2 in mice with streptozotocin-induced diabetic nephropathy as well as that of amplification of circulating ACE2 using minicircle DNA delivery prior to induction of experimental diabetes. This delivery resulted in a long-term sustained and profound increase in serum ACE2 activity and enhanced ability to metabolize an acute angiotensin II (1-8) load. In mice with streptozotocin-induced diabetes pretreated with minicircle ACE2, ACE2 protein in plasma increased markedly and this was associated with a more than 100-fold increase in serum ACE2 activity. However, minicircle ACE2 did not result in changes in urinary ACE2 activity as compared to untreated diabetic mice. In both diabetic groups, glomerular filtration rate increased significantly and to the same extent ascompared to non-diabetic controls. Albuminuria, glomerular mesangial expansion, glomerular cellularity, and glomerular size were all increased to a similar extent in minicircle ACE2-treated and untreated diabetic mice, as compared to non-diabetic controls. Recombinant mouse ACE2 given for 4 weeks by intraperitoneal daily injections in mice with streptozotocin-induced diabetic nephropathy also failed to improve albuminuria or kidney pathology. Thus, a profound augmentation of ACE2 confined to the circulation failed to ameliorate the glomerular lesions and hyperfiltration characteristic of early diabetic nephropathy. These findings emphasize the importance of targeting thekidney rather than the circulatory renin angiotensin system to combat diabetic nephropathy.

Serum activity of angiotensin converting enzyme 2 is decreased in patients with acute ischemic stroke.

Levels of angiotensin converting enzyme 2 (ACE2), a cardio and neuro-protective carboxypeptidase, are dynamically altered after stroke in preclinical models. We sought to characterize the previously unexplored changes in serum ACE2 activity of stroke patients and the mechanism of these changes. Serum samples were obtained from patients during acute ischemic stroke (n=39), conditions mimicking stroke (stroke-alert, n=23), or from control participants (n=20). Enzyme activity levels were analyzed by fluorometric assay and correlated with clinical variables by regression analyses. Serum ACE2 activity was significantly lower in acute ischemic stroke as compared to both control and stroke-alert patients, followed by an increase to control levels at three days. Serum ACE2 activity significantly correlated with the presence of ischemic stroke after controlling for other factors (P=0.01). Additional associations with ACE2 activity included a positive correlation with systolic blood pressure at presentation in stroke-alert (R2=0.24, P=0.03), while stroke levels showed no correlation (R2=0.01, P=0.50). ACE2 sheddase activity was unchanged between groups. These dynamic changes in serum ACE2 activity in stroke, which concur with preclinical studies, are not likely to be driven primarily by acute changes in blood pressure or sheddase activity. These findings provide new insight for developing therapies targeting this protective system in ischemic stroke.

Serum angiotensin-converting enzyme 2 is an independent risk factor for in-hospital mortality following open surgical repair of ruptured abdominal aortic aneurysm.

Open surgical repair (OSR) is a conventional surgical method used in the repair a ruptured abdominal aortic aneurysm (AAA); however, OSR results in high perioperative mortality rates. The level of serum angiotensin-converting enzyme 2 (ACE2) has been reported to be an independent risk factor for postoperative in-hospital mortality following major cardiopulmonary surgery. In the present study, the association of serum ACE2 levels with postoperative in-hospital mortality was investigated in patients undergoing OSR for ruptured AAA. The study enrolled 84 consecutive patients underwent OSR for ruptured AAA and were subsequently treated in the intensive care unit. Patients who succumbed postoperatively during hospitalization were defined as non-survivors. Serum ACE2 levels were measured in all patients prior to and following the surgery using ELISA kits. The results indicated that non-survivors showed significantly lower mean preoperative and postoperative serum ACE2 levels when compared with those in survivors. Multivariate logistic regression analysis also showed that, subsequent to adjusting for potential confounders, the serum ACE2 level on preoperative day 1 showed a significant negative association with the postoperative in-hospital mortality. This was confirmed by multivariate hazard ratio analysis, which showed that, subsequent to adjusting for the various potential confounders, the risk of postoperative in-hospital mortality remained significantly higher in the two lowest serum ACE2 level quartiles compared with that in the highest quartile on preoperative day 1. In conclusion, the present study provided the first evidence supporting that the serum ACE2 level is an independent risk factor for the in-hospital mortality following OSR for ruptured AAA. Furthermore, low serum ACE2 levels on preoperative day 1 were found to be associated with increased postoperative in-hospital mortality. Therefore, the serum ACE2 level on preoperative day 1 may be a potential biomarker or prognostic factor for in-hospital mortality following OSR for ruptured AAA.

Abstract TP214: Serum Activity of Angiotensin Converting Enzyme 2 is Decreased During Ischemic Stroke in Humans

Introduction: Abundant preclinical studies show efficacy for therapies targeted to the protective axis of the renin-angiotensin system in stroke. The expression and activity of angiotensin converting enzyme 2 (ACE2), a cardio and neuro-protective carboxypeptidase in this axis, have recently been shown to be dynamically altered during stroke in animal models. Hypothesis: The aim of this study was to characterize the previously unexplored changes in activity of ACE2, and other RAS enzymes, in the serum of patients experiencing acute ischemic stroke. Methods: Blood samples were obtained from patients with acute ischemic stroke (n=20) at presentation and again at three days post-stroke and enzyme activity levels in isolated serum were analyzed by fluorometric assay. These were compared to enzyme activity levels in samples obtained from a cohort of patients presenting with transient ischemic attack or other clinical presentations mimicking stroke and from healthy control participants (n=20). Results: Ischemic stroke resulted in significantly lower levels of serum ACE2 activity at an average of 3.5 hours after stroke as compared to both transient ischemic attack/stroke mimic and healthy control participant levels, followed three days later by an increase back to control levels. ACE activity was also significantly decreased following stroke, but without increases at three days. Renin enzyme activity during stroke did not significantly differ from controls at either time point. Serum ACE2 activity was negatively correlated with systolic blood pressure at presentation among stroke patients, while activity levels from a separate cohort of healthy young adults were positively correlated. Multiple regression analyses indicated that ACE2 activity levels were significantly correlated with a diagnosis of ischemic stroke, with those in the lowest tertile of all participants were at 7.7 times increased odds of having had a stroke. Conclusions: The characterization of the dynamic and novel changes in serum ACE2 activity in human stroke, which concur with preclinical studies, along with the demonstration of correlations with systolic blood pressure, provides new insight for the development of therapies that target this protective system in ischemic stroke.

Abstract 12650: Activity of Serum Angiotensin Converting Enzyme 2 is Decreased During Acute Ischemic Stroke in Humans

Introduction: The expression and activity of angiotensin converting enzyme 2 (ACE2), a cardio and neuro-protective carboxypeptidase, has recently been shown to be dynamically altered during and after stroke in animal models. Hypothesis: The aim of this study was to characterize the previously unexplored changes in activity of ACE2 in the serum of patients experiencing acute ischemic stroke. Methods: Serum samples were obtained from patients presenting with acute ischemic stroke (n=20) and again at three days post-stroke and enzyme activity levels were analyzed by fluorometric assay and compared to levels from non-stroke control patients (n=20). Results: Ischemic stroke resulted in a significant decrease in serum ACE2 at an average of 3.5 hours after stroke, which was followed by a rebound increase by three days later (Fig 1). ACE activity was also significantly decreased following stroke, but without rebound increases. Tumor necrosis factor-alpha converting enzyme activity was not significantly different from control. ACE2 activity was negatively correlated with systolic blood pressure (SBP) among stroke patients (Fig 2), while activity was positively correlated with SBP among a cohort of healthy young adults (n=16). Conclusions: The characterization of the dynamic and novel changes in serum ACE2 activity in human stroke, which follow observations from preclinical studies, along with the demonstration of a negative association with SBP, provides new insight for the development of therapies that target this protective system in the context of ischemic stroke. Data are mean ± SEM. RFU: relative fluorescence units; *p&lt;0.001 vs. control; †p&lt;0.05 vs. 4h post stroke.

Mesenchymal Stem Cells Overexpressing Angiotensin-Converting Enzyme 2 Rescue Lipopolysaccharide-Induced Lung Injury

Bone marrow-derived mesenchymal stem cells (MSCs), which have beneficial effects in acute lung injury (ALI), can serve as a vehicle for gene therapy. Angiotensin-converting enzyme 2 (ACE2), a counterregulatory enzyme of ACE that degrades angiotensin (Ang) II into Ang 1-7, has a protective role against ALI. Because ACE2 expression is severely reduced in the injured lung, a therapy targeted to improve ACE2 expression in lung might attenuate ALI. We hypothesized that MSCs overexpressing ACE2 would have further benefits in lipopolysaccharide (LPS)-induced ALI mice, when compared with MSCs alone. MSCs were transduced with ACE2 gene (MSC-ACE2) by a lentiviral vector and then infused into wild-type (WT) and ACE2 knockout (ACE2(-/y)) mice following an LPS-induced intratracheal lung injury. The results demonstrated that the lung injury of ALI mice was alleviated at 24 and 72 h after MSC-ACE2 transplantation. MSC-ACE2 improved the lung histopathology and had additional anti-inflammatory effects when compared with MSCs alone in both WT and ACE2(-/y) ALI mice. MSC-ACE2 administration also reduced pulmonary vascular permeability, improved endothelial barrier integrity, and normalized lung eNOS expression relative to the MSC group. The beneficial effects of MSC-ACE2 could be attributed to its recruitment into the injured lung and enhanced local expression of ACE2 protein without changing the serum ACE2 levels after MSC-ACE2 transplantation. The biological activity of the increased ACE2 protein decreased the Ang II amount and increased the Ang 1-7 level in the lung when compared with the ALI and MSC-only groups, thereby inhibiting the detrimental effects of accumulating Ang II. Therefore, compared to MSCs alone, the administration of MSCs overexpressing ACE2 resulted in a further improvement in the inflammatory response and pulmonary endothelial function of LPS-induced ALI mice. These additional benefits could be due to the degradation of Ang II that accompanies the targeted overexpression of ACE2 in the lung.

Association Between Angiotensin-Converting Enzyme 2 and Coronary Artery Calcification in Patients on Maintenance Hemodialysis Therapy.

While all mechanisms that contribute to the pathogenesis of coronary artery calcification (CAC) are unknown, angiotensin-converting enzyme 2 (ACE2) may be involved in this process in maintenance hemodialysis (MHD) patients. The aim of this study was to investigate the association between ACE2 and CAC in patients on MHD therapy. Ninety patients on MHD therapy were involved in this prospective study. CAC was quantified by CAC score (CACs) using the Agatston method and a multi-slice CT scanner. Univariate and multivariate logistic regression were used to analyze the association between ACE2 and CACs. In the univariate analysis, CACs positively correlated with ACE2 (r = 0.666, P < 0.001). After adjusting for age, sex, smoking, hypertension, body mass index, diabetes mellitus, and hyperlipidemia, ACE2 levels continued to significantly and independently predict the presence of CAC. ROC curve analysis showed that the serum ACE2 level can predict the extent of CAC. These findings indicate that elevated serum ACE2 may be involved in vascular calcification in patients receiving MHD therapy.