COVID-19 and Diabetes: What Should We Expect?

Patients with diabetes are at increased risk of the severe course of the coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We read with great interest the article of Pfützner et al.¹ in the Journal of Diabetes Science and Technology (JDST). The authors pointed out the relationship between periodontal diseases, diabetes, and increased COVID-19 mortality. Along with the possibility of salivary gland infection, some reports on the literature have also shown hyposalivation and taste alterations in COVID-19 patients. In this letter, we would like to call the attention of the possible long-term oral consequences that individuals affected by COVID-19 may present, especially regarding diabetes.

The SARS-CoV and the SARS-CoV-2 share similarities. Both viruses use angiotensin-converting enzyme 2 (ACE-2) as receptor for entry into target cells and transmembrane serine protease 2 for priming.² ACE-2 is expressed in several tissues, including salivary glands and pancreas. In the pancreas, the previous SARS-CoV was found to damage islets, reduce insulin release, and cause acute insulin-dependent diabetes mellitus.³ It was reported that, after hospitalization, more than 50% of the patients with SARS-CoV infection became diabetic.³ Interestingly, the SARS-CoV-2 infection was shown to cause ketosis or ketoacidosis and induced diabetic ketoacidosis for those with diabetes.⁴ The SARS-CoV-2 could also infect and cause damage to α-cells and β-cells of the pancreas, aggravating its function.^5,6 Thus, it is possible that COVID-19 trigger diabetes in some individuals.

Literature reports that patients with diabetes often present oral repercussions, including periodontal diseases and salivary gland dysfunction, among others. It is well known that oxidative stress plays an important role in diabetes. Oxidative stress has also been suggested as a link between diabetes and periodontal disease. Interestingly, literature also suggested oxidative stress as a player in COVID-19 infection. According to our group experience, the salivary glands present oxidative damage and disturbances in the metabolism and antioxidant system as a result of the hyperglycemia in the diabetic state. Along with the direct effect of the SARS-CoV-2 infection in the pancreas and salivary glands, this could also contribute to explain the qualitative and quantitative alterations in the saliva of diabetic and COVID-19 patients and thus, the oral repercussions reported.

Overall, studies are still necessary to unveil the oral consequences of COVID-19 in a long term as well as the development of metabolic disorders such as diabetes, which could have a significant impact on general and dental practice. This is not only relevant due to the increased risk of COVID-19 short-term complications but also because patients with diabetes and other systemic disorders seeking treatment may increase due to COVID-19 infection.