Diabetes develops when the body’s ability to regulate blood glucose levels breaks down. It can either result from damage to beta cells in the pancreas that produce the hormone insulin, known as type 1 diabetes, or from the body becoming insensitive to the hormone, which leads to type 2 diabetes.
A panel of 17 diabetes specialists from around the world suspect that there is a two-way relationship between diabetes and COVID-19.
In a letter to The New England Journal of Medicine, they write that while experts know that having diabetes can increase a person’s risk of severe COVID-19, some evidence shows that people may develop diabetes for the first time as a result of the infection.
The specialists note that COVID-19 can cause severe metabolic complications in people with diabetes, necessitating treatment with exceptionally high doses of insulin.
They also cite a case report from a hospital in Singapore of a previously healthy man who developed diabetic complications after contracting COVID-19.
In addition, a study in 2010 of 39 patients who were receiving treatment for severe acute respiratory syndrome (SARS) in a Chinese hospital indicated that 20 of these hospitalized patients developed diabetes for the first time.
SARS-CoV-1, a coronavirus closely related to SARS-CoV-2, causes SARS. Both viruses gain entry to human cells via the same receptor, known as ACE2 (angiotensin-converting enzyme 2).
In their letter, the diabetes specialists point out that many key metabolic tissues in the body, including beta cells in the pancreas, adipose (fat storage) tissue, the small intestine, and kidneys, contain ACE2 receptors.
They believe that when these viruses bind to ACE2 receptors, they may trigger changes in glucose metabolism that worsen preexisting diabetes or cause the condition to develop for the first time.
The specialists have set up the CoviDiab Registry to gather data on the problem from doctors to establish its extent and how best to treat it.
“Diabetes is one of the most prevalent chronic diseases, and we are now realizing the consequences of the inevitable clash between two pandemics,” says Francesco Rubino, professor of metabolic surgery at King’s College London in the United Kingdom and co-lead investigator of the project.
“Given the short period of human contact with this new coronavirus, the exact mechanism by which the virus influences glucose metabolism is still unclear, and we don’t know whether the acute manifestation of diabetes in these patients represents classic type 1, type 2, or possibly a new form of diabetes.”
One of the most important questions will be whether patients who develop diabetes in this way remain at higher risk for the condition after leaving the hospital.
Paul Zimmet, professor of diabetes at Monash University in Melbourne, Australia, and a co-lead investigator in the project says: “We don’t yet know the magnitude of new-onset diabetes in COVID-19 and if it will persist or resolve after the infection, and if so, whether or not COVID-19 increases risk of future diabetes.
“By establishing this global registry, we are calling on the international medical community to rapidly share relevant clinical observations that can help answer these questions.”
Some of the experts the Science Media Centre in London approached for comment expressed skepticism that COVID-19 can cause diabetes.
Dr. Gabriela da Silva Xavier, senior lecturer in cellular metabolism at the University of Birmingham in the U.K., said the evidence cited in the letter was insufficient to prove a causal link. However, she supported the authors’ call for more data.
“In short, it would be unfair to take the cited data to indicate that COVID-19 is causal of diabetes and diabetes complications,” she said. “But, given the observations, it is reasonable to propose to look at this carefully, as proposed in the letter.”
Dr. Riyaz Patel, associate professor of cardiology & consultant cardiologist at University College London Hospital in the U.K., also backed the registry. But he emphasized that there is currently no robust evidence of a causal link between COVID-19 and diabetes:
“Observational data linking the two may be confounded for a few reasons. For example, we know that any stress-inducing illness can cause blood sugar levels to temporarily rise, and we see this, for example, with heart attacks. Also, people who are more likely to get very sick with COVID may be at risk of developing diabetes anyway, perhaps because they are overweight. We know that obesity is linked to worse outcomes with COVID.”
Naveed Sattar, a professor of metabolic medicine at the University of Glasgow in the U.K., said it would take 1–2 years to confirm whether overall rates of diabetes in populations have increased as a result of the pandemic.
“In the meantime,” he said, “people should be encouraged to keep active and eat healthily, or as best they can, to keep their weights stable or to lose a few pounds to lessen their risks of diabetes now — and in the future — and potentially to reduce their risks of developing more severe COVID-19, should they succumb to the infection.”
