The concentration of angiotensin-converting enzyme 2 (ACE2) in the blood of men is higher than that of women, reports a research team from the University of Groningen Medical Center in the Netherlands. The coronavirus infects cells using the ACE2 enzyme. It is the difference in its concentration in the blood that may explain why men are more vulnerable to COVID-19, writes the European Heart Journal. The study included the data of over 3,700 people. ACE2 is a receptor that is found on the surface of the cell. The SARS-CoV-2 virus binds to it and thus manages to penetrate the cell. High levels of ACE2 are found in lung tissue, which plays a crucial role in the rapid progression of the coronavirus infection. The different blood markers in the two sexes have been studied since before the current coronavirus pandemic. This allows a quick start for researchers to collect and analyze data from the beginning of the pandemic wave with the new coronavirus. The researchers measured the concentration of ACE2 in blood samples of two groups of heart failure patients from 11 European countries. With the research of the first group, the scientists verified the truth of their hypothesis. It included 1485 men with an average age of 69 years and 537 women with an average age of 75 years. They confirmed their conclusion with the data from the second control group, consisting of 1123 men and 575 women with an average age of 74 and 76 years, respectively. When analyzing the data, which included clinical factors affecting ACE2 concentration, including the use of receptor inhibitors, a history of COPD, coronary artery disease and atrial fibrillation, the researchers found that male gender was the strongest risk factor for increased enzyme concentration. By the way, its presence was found in other tissues of the body – in the heart, kidneys, endothelial cells of blood vessels, especially high levels of it were found in the testicles. It is the latter fact that gives the researchers reason to suggest that the regulation of the enzyme in the testes, at least in part, may explain the higher concentration of ACE2 in men and their greater vulnerability to covid. In addition, the team recorded that in patients with heart failure treated with certain medications, the concentration of the enzyme was not high. These were renin-angiotensin-aldosterone (RAAS), ACE inhibitors or angiotensin receptor blockers (ARBs). According to the head of the team, Dr. Adrian Voors, this provoked to investigate how the intake of these drugs affects the condition of patients infected with the coronavirus with heart failure. Results from previous research indicate that RAAS inhibitors can increase the concentration of ACE2 in the blood plasma, increasing the risk of contracting the coronavirus for those taking them. The new study shows that this is not quite the case, but further research is needed to look not only at the concentration of the enzyme in plasma, but also in tissues.which is a more accurate indicator of risk, the team commented. In addition, stopping these drugs seriously increases the likelihood of a fatal outcome in patients with heart failure, they commented. A doctor’s assessment of the patient’s benefit and risk becomes doubly complicated because it must be considered relative to their underlying disease and relative to COVID-19.