Reporting in Cell Metabolism, an international team of researchers has suggested that COVID-19 has caused diabetes in some patients. While diabetics are thought to be at risk for more severe SARS-CoV-2 infections, this research has indicated that in severe cases, the virus may also cause the metabolic disease. A few studies have reported that about 15 percent of people that are hospitalized with COVID-19 are also newly diagnosed with diabetes.
In this study, the scientists found that SARS-CoV-2 is able to infect pancreatic beta cells directly. These are the only cells in the body that are known to produce insulin, which regulates the level of blood sugar in the blood. Type 1 diabetics lack beta cells. In type 2 diabetes, the system stops working in some way; beta cells stop producing the hormone insulin, for example, or the body may become resistant to its effects. In either type of diabetes, the loss of insulin can lead to dangerous fluctuations in blood sugar levels.
SARS-CoV-2 can use a receptor called ACE2 on the surface of respiratory cells to infect them. Beta cells don't have many of these receptors, however. The researchers examined post-mortem tissue samples from seven COVID-19 patients and revealed the presence of SARS-CoV-2 in the patients' pancreatic beta cells, so the virus clearly found a way into those cells. There were also high levels of a protein called neuropilin-1 (NRP1) in the beta cells; the researchers suggested that NRP1 may be another way for the virus to infect them.
Additional work using beta cells growing in culture suggested that infected beta cells generate less insulin and show signs of imminent death. When neuropilin-1 activity was chemically blocked, the virus wasn't as infectious in this cell type. The researchers want to know whether this approach might help patients with severe COVID-19. More work will also be needed to determine how the virus reaches the pancreas.
“Current research cannot say for sure whether sugar metabolism normalizes again in all COVID-19 patients after an infection, or whether and how often permanent diabetes may develop,” said Dr. Matthias Matter of the University of Basel and the University Hospital Basel. Patients that survive the infection will have to be monitored.
Matter added that there is evidence that so-called “long COVID” patients show signs of diabetes for several weeks to months afterwards their infection, and these people may benefit greatly from therapeutics that prevent lasting damage.