APOE also regulates fat transport and cholesterol homeostasis in the brain10, and several studies have shown the association between APOE polymorphisms and diseases such as Alzheimer's disease11, cardiovascular disease12, type 2 diabetes (T2DM)13 and brain vascular pathologies14, which are comorbidities related to SARS-CoV-2 severity. Here, APOE is linked to type 2 diabetes mellitus.