Clash of the two titans - COVID-19 and type 2 diabetes mellitus

COVID-19 has infected more than 32 million people globally in more than 100 countries. Diabetes mellitus (DM) has emerged as an important factor involved in the fatal outcomes of COVID-19. Accumulating evidence suggests that that reciprocal relationship may exist between these two raging pandemics, thus making COVID-19 more challenging for people with diabetes. Furthermore, poorly managed glycaemia in diabetes patients leads to increased risk of severe complications and higher mortality rate. The association between COVID-19 severity and DM can be supported by several pathophysiological mechanisms, such as compromised innate immune system, deranged cell-mediated immunity and adipose tissue infiltration of pro-inflammatory macrophages. Exaggerated coagulation and pro-thrombotic milieu in diabetes can predispose to thromboembolic complications associated with fatal outcomes in diabetic patients with COVID-19. Impaired pulmonary function and elevated levels of furin associated with diabetes can increase the chances of COVID-19 infection in patients with diabetes. In addition, SARS-CoV-2 infection can trigger stress hyperglycaemia leading to augmented viral replication and severity of infection associated with poor clinical outcomes in diabetic patients with COVID-19. Endothelial dysfunction associated with virus-induced endothelialitis can lead to organ ischaemia and life-threatening complications associated with COVID-19 with underlying DM. Vitamin D deficiency and insulin resistance worsened by SARS-CoV2 can lead to higher mortality and morbidity observed in diabetic patients with COVID-19. Therefore, COVID-19 patients should be adequately monitored for the development of new-onset diabetes, due to deranged glycaemic control, owing to underlying COVID-19 disease, and diabetic patients with COVID-19 should be kept under strict glycaemic control to avoid life-threatening complications.