Patients with severe COVID‐19 have reduced circulating levels of angiotensin‐(1–7): A cohort study

Abstract Background and Aims Angiotensin‐converting enzyme 2 (ACE2) acts as a functional receptor for the entry of severe acute respiratory syndrome coronavirus 2 into host cells. Angiotensin (1–7) (Ang (1–7)) obtained from the function of ACE2 improves heart and lung function. We investigated the relationship between Ang (1–7) level and disease severity in patients with coronavirus disease 2019 (COVID‐19). Methods This cohort study was carried out at Masih Daneshvari Hospital in Tehran, Iran from September 2020 to October 2020. To do so, the Ang (1–7) levels of 331 hospitalized COVID‐19 patients with and without underlying disease were measured by ELISA kit. The need for oxygen, intubation, and mechanical ventilation were recorded for all the patients. Results Results showed a significant inverse relationship between the levels of Ang 1–7 and the severity of the disease (needed oxygen, intubation, and mechanical ventilation). According to the results, median (interquartile range) of Ang (1–7) levels was significantly lower in patients who needed oxygen versus those who needed no oxygen (44.50 (91) vs. 82.25 (68), p = 0.002), patients who needed intubation and mechanical ventilation versus those who did not (9.80 (62) vs. 68.70 (102), p < 0.000) and patients hospitalized in an intensive care unit (ICU) than people hospitalized in other wards. We also found that the older patients were more in need of ICU and mechanical ventilation than younger patients. Conclusions Higher levels of Ang (1–7) have been associated with decreased disease severity. Besides this, we perceived that synthetic Ang 1–7 peptides may be useful to treat and reduce the complications of COVID‐19.


| INTRODUCTION
As a newfound illness, coronavirus disease 2019 (COVID- 19) pneumonia is rapidly spreading around the world. The renin-angiotensin-aldosterone system plays a critical role in COVID-19 pathogenesis.
Recent studies have shown a crucial role of angiotensinconverting enzyme 2 (ACE2) in the pathogenesis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, which causes COVID-19. ACE2 acts as a functional receptor for the entry of SARS-CoV-2 into host cells. ACE2 as a membrane-bound aminopeptidase converts angiotensin I (Ang I) and Ang II into Ang (1-9) and (Ang 1-7), respectively, and is expressed in various human organs. 1 Ang (1-7) exerts vasodilation, vascular protection, anti-fibrosis, antiproliferation, and anti-inflammation actions. The heart, brain, and kidney are major sources to produce Ang (1)(2)(3)(4)(5)(6)(7). This peptide as a vasodilator agent plays an important role in improving heart and lung functions. 2 On the one hand, ACE2 is overexpressed in heart failure, arterial hypertension, and diabetes mellitus. So, people with these underlying diseases are more likely to get infected by COVID-19. On the other hand, SARS-CoV-2 downregulates ACE2 and reduces Ang (1-7) after infection. As a result, the high severity and high mortality rate among these patients could be due to reasons, such as vasoconstriction, vascular damage, fibrosis, proliferation, and inflammation due to reduction of Ang (1-7). 3 Given the key role of ACE2 in infection of the virus and the protective roles of Ang (1-7) as its product, we hypothesized that there was an indirect relationship between Ang (1-7) level and disease severity in patients with COVID-19.
However, no reports are available regarding Ang (1-7) levels in the COVID-19 patients with various disease severities. Therefore, in this study, we evaluated the relationship between Ang (1-7) levels and disease severity in the COVID-19 patients with and without the underlying diseases, such as cardiovascular diseases and diabetes.

| Biochemical assessments and clinical symptoms
The blood samples of all the subjects were first taken immediately after the patients were admitted to the hospital when it was    patients. 24 Monteil 25 reported that soluble ACE2 might block SARS-CoV-2 infections in the early stages, but it has no efficacy when the COVID19 disease becomes more severe.
In this study, moreover, disease severity and Ang 1-7 levels were not different between male and female patients. In an investigation on 99 patients infected with SARS-CoV-2, Chen et al. 26 showed that males were more susceptible to infection than females because ACE2-expressing lung cells were more abundant in males. Li et al. 27 also indicated that SARS-CoV-2 may equally infect individuals of different sexes, ages, and races. They further pointed out that the disease severity in people of different ages and gender depends on the host immune response to SARS-CoV-2 infection.
One of the limitations of this study was the nonparticipation of non-COVID-19 volunteers and COVID-19 patients who did not need to be hospitalized, as well as those who unfortunately died of this disease.
The other limitation was the lack of peptide assay by gold-standard methods such as liquid chromatography-tandem mass spectrometry.
The lack of matching of factors such as age, sex, and BMI was another limitation of this study; however, the amount of Ang (1-7) in different groups of age, sex, and BMI in this study was not different.

| CONCLUSION
In the current research, we firstly found that there is a significant and indirect relationship between Ang (1-7) levels and the severity of COVID-19 disease, both in patients with and without underlying diseases. Therefore, further studies, especially randomized controlled clinical trials are needed to clearly delineate the benefits of Ang (1)(2)(3)(4)(5)(6)(7) actions in COVID 19 patients.

ACKNOWLEDGMENTS
The authors deeply thank all the patients who participated in the present study. This study was supported by Arak University of Medical Sciences, Arak, Iran (grant number 3691) and Shahid Beheshti University of Medical Sciences, Tehran, Iran (grant number 153).

CONFLICTS OF INTEREST
The authors declare no conflicts of interest.

ETHICS STATEMENT
This study was approved by the human research ethics committee at