SIRT1 and COVID-19: Although our initial results demonstrated significant downregulation of HIF1A and GLUT1 in NK cells from patients with severe COVID-19 compared to healthy controls, further stratification by clinical outcome revealed that patients with fatal outcomes exhibited elevated expression of SIRT1, HIF1A, and GLUT1. This finding aligns with previous reports linking HIF1A expression to poorer clinical outcomes (Codo et al., 2020; Tian et al., 2021; Karabulut Uzunçakmak et al., 2022).