mRNA, ACE2, and TMPRSS2 proteins are highly expressed in human pancreatic islets and ductal and acinar cells, and according to a study by [41], type 1 diabetes mellitus (DM1) in children in the United Kingdom first increased during the COVID-19 pandemic, thereby creating a connection between severe COVID-19 and increased blood glucose levels. This evidence concerns the gene TMPRSS2 and diabetes mellitus.