MMP9 and COVID-19: These data suggest possible links between MMP-9 and lipid metabolism in COVID-19, which is not surprisingly based on previous (COVID-19-unrelated) studies by many investigators including our group (for MMP-2, MMP-7, and MMP-9, as well as their tissue inhibitors TIMP-2 and TIMP-3) [14,78,98,99,100,101,102,103].