Patients with pre-existing chronic diseases are more susceptible to coronavirus disease 2019 (COVID-19), yet the underlying causes of increased risk are of infection remain unclear. Angiotensin-converting- enzyme 2 (ACE2), the cell surface receptor that recognizes the coronavirus spike protein has protective effects against inflammation and chronic hyperglycemia in animal models. The roles of ACE2 in severe SARS-CoV-2 infections remains ambiguous due to contradictory findings. In this study, we aimed to investigate the relationship between human plasma ACE2 levels in diabetics and the high risk of severe SARS-CoV-2 infection. First, the medical records of 245 patients with SARS-CoV-2-positive who have chronic diseases were analyzed. We also recruited 404 elderly subjects with comorbid chronic diseases such as diabetes mellitus, coronary heart disease, cerebrovascular disease, hypertension and obesity, and investigated the ACE2 plasma levels. Plasma concentrations of ACE2 were much lower (2973.83±2196.79 pg/mL) in diabetics with chronic disease than in healthy controls (4308.21±2352.42 pg/ml), and the use of hypoglycemia drugs was associated with lower circulating concentrations of ACE2 (P=1.49E-08). Diabetics with lower plasma levels of ACE2 may be susceptible to severe COVID-19. Our findings suggest that the poor prognosis in patients with diabetes infected with SARS-CoV-2 may be due to low circulating ACE2 levels.
Keywords: COVID-19; angiotensin-converting enzyme 2; diabetes.