Angiotensin I-converting enzyme type 2 expression is increased in pancreatic islets of type 2 diabetic donors

Aims: Angiotensin I-converting enzyme type 2 (ACE2), a pivotal SARS-CoV-2 receptor, has been shown to be expressed in multiple cells, including human pancreatic beta-cells. A putative bidirectional relationship between SARS-CoV-2 infection and diabetes has been suggested, confirming the hypothesis that viral infection in beta-cells may lead to new-onset diabetes or worse glycometabolic control in diabetic patients. However, whether ACE2 expression levels are altered in beta-cells of diabetic patients has not yet been investigated. Here, we aimed to elucidate the in situ expression pattern of ACE2 in Type 2 diabetes (T2D) with respect to non-diabetic donors which may account for a higher susceptibility to SARS-CoV-2 infection in beta-cells.

Material and methods: Angiotensin I-converting enzyme type 2 immunofluorescence analysis using two antibodies alongside insulin staining was performed on formalin-fixed paraffin embedded pancreatic sections obtained from n = 20 T2D and n = 20 non-diabetic (ND) multiorgan donors. Intensity and colocalisation analyses were performed on a total of 1082 pancreatic islets. Macrophage detection was performed using anti-CD68 immunohistochemistry on serial sections from the same donors.

Results: Using two different antibodies, ACE2 expression was confirmed in beta-cells and in pancreas microvasculature. Angiotensin I-converting enzyme type 2 expression was increased in pancreatic islets of T2D donors in comparison to ND controls alongside with a higher colocalisation rate between ACE2 and insulin using both anti-ACE2 antibodies. CD68⁺ cells tended to be increased in T2D pancreata, in line with higher ACE2 expression observed in serial sections.

Conclusions: Higher ACE2 expression in T2D islets might increase their susceptibility to SARS-CoV-2 infection during COVID-19 in T2D patients, thus worsening glycometabolic outcomes and disease severity.