DPP4 and type 2 diabetes mellitus: If DPP-4 is a coreceptor for SARS-CoV-2, considering that severity and poor prognosis in COVID-19 are associated with T2D and hyperglycemia, conditions in which DPP-4 is not well regulated, inhibition of DPP-4 could be an alternative therapy for improving metabolic control and prognosis in COVID-19 patients.