ABSTRACT
INTRODUCTION: Currently, diabetes mellitus (DM), as well as coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), are major public health issues worldwide. BACKGROUND: It has been suggested that patients with DM are more vulnerable to SARS-CoV-2 infection and suffer from more severe forms of the disease. METHODS: A literature search was performed using PubMed, Scopus, and Google search engines. RESULTS: Angiotensin-converting enzyme-2 (ACE2) is the major receptor of SARS-CoV-2 in the human host. The differential expression of ACE2 in the lungs of patients with DM makes them more susceptible to COVID-19. Additionally, acute or chronic hyperglycemia renders individuals in an immune-suppressive state, with impaired innate and adaptive immunity function, also contributing to the severity of COVID-19 infection among patients with DM. Other factors contributing to a more severe course of COVID-19 include the coexistence of obesity in T2DM, the endothelial inflammation induced by the SARS-CoV-2 infection, which aggravates the endothelial dysfunction observed in both T1DM and T2DM, and the hypercoagulability presented in COVID-19 infection that increases the thrombotic tendency in DM. CONCLUSION: This review summarizes the pathophysiologic mechanisms underlying the coexistence of both pandemics as well as the current recommendations and future perspectives regarding the optimal treatment of inpatients and outpatients with DM in the era of SARS-CoV-2 infection. Notably, the currently recommended drugs for the treatment of severe COVID-19, dexamethasone and remdesivir, may cause hyperglycemia, an adverse effect that physicians should bear in mind when caring for patients with DM and COVID-19.