Is there a link between COVID-19 and Diabetes?

One of the mysteries of COVID-19 is why the infection can cause extreme reactions such as a life-threatening inflammatory response, high fevers, and breathing issues in some people, while other individuals experience few or no symptoms at all. COVID-19 has shown doctors, patients, and researchers alike that it’s not like other viruses-it’s been known to cause severe inflammation throughout the body, wreaking havoc not only on the respiratory system, but also the heart, brain, and kidneys, among other essential organs. Now, more research points to another “troubling” effect of COVID-19: new cases of diabetes.

Part of that focus centers on a disturbing trend that has critical care doctors and endocrinologists searching for clues — and answers — about why some individuals with COVID-19 suddenly develop type 1 and type 2 diabetes.

Initially when the pandemic started in 2020, doctors noticed that a high percentage of COVID-19 patients had diabetes, Mihail Zilbermint, MD, an assistant professor of medicine at the division of endocrinology, diabetes, and metabolism at the Johns Hopkins School of Medicine in Baltimore. “At first this was observed in China because those were the majority of patients who were initially hospitalized,” he says.

Originally, the thought was that diabetes would only increase the risk of getting or having a more severe case of COVID-19, but now it appears as though there may be some sort of bidirectional relationship between diabetes and COVID-19. Research is still ongoing to further solidify this link between COVID-19 infections and new diabetes diagnoses.

Diabetes is a disease that happens when your blood glucose (aka blood sugar) is too high, according to the National Institute for Diabetes and Digestive and Kidney Diseases (NIDDK). It’s a condition that affects an estimated 30.3 million people in US (that’s about 9.4% of the population).

Blood glucose is your body’s main source of energy and comes from the food you eat. Typically, that glucose is escorted to your cells by insulin, a hormone made by your pancreas, where the glucose will be used for energy, NIDDK explains. But with diabetes, a person’s body doesn’t make insulin or doesn’t use it well. That means the glucose that is supposed to be transported to cells stays in the person’s blood-and that can cause a range of serious health issues, like heart disease, nerve damage, eye problems, and kidney disease.

Scientists have long known that exposure to viruses can be a possible trigger for type 1 diabetes, and they have no reason to believe that the virus that causes COVID-19 is any different.

The theory involves a cellular receptor called angiotensin-converting enzyme 2, commonly called ACE2 receptor. This is the protein that allows the coronavirus to infect human cells. ACE2 receptors are located in many parts of the body: the upper and lower respiratory tract, the heart, the kidneys, and parts of the gastrointestinal tract.

The SARS-CoV-2 virus, or the so-called novel coronavirus, which causes COVID-19, binds to ACE2 before it enters and infects the cells, according to the Children’s Hospital of Philadelphia.

The ACE 2 receptor is also located on and in those cells of the pancreas. If a person gets infected and has the virus in their body, it appears that the virus can enter the pancreas and seek out those cells and destroy them, says Lazar. “That doesn’t happen to everyone. We are still trying to figure out the real numbers on this, but it definitely is happening,” he says.

An Editorial published in Diabetes, Obesity, Metabolism in November 2020-technically a systematic review and meta-analysis-analyzed data from eight studies conducted around the world between January and May 2020 of newly-diagnosed cases of diabetes in people who had COVID-19. The analysis looked at 3,711 patients with COVID-19 and found that 14.4% (or 492 patients) were recently diagnosed with diabetes. (The exact type wasn’t always clear-just one of the studies specified the type of diabetes patients were diagnosed with, and that was type 2 diabetes.)

It’s worth noting that this specific research showed only an association between COVID-19 infections and new diabetes diagnoses, not a causal link. But according to researchers, it still rang alarm bells. “While newly diagnosed diabetes in COVID-19 patients could be attributed to the stress response associated with severe illness or treatment with glucocorticoids, the diabetogenic effect of COVID-19 should also be considered,” researchers wrote, adding that COVID-19 patients with newly-diagnosed diabetes “should be managed early and appropriately and closely monitored for the emergence of full-blown diabetes and other cardiometabolic disorders in the long term.”

The two new NIH-supported studies-one shared in Cell Metabolism on May 19, the other on May 18-took deeper look at the connection between COVID-19 and diabetes, this time from within the body.

Previously, per the NIH blog, lab studies found that the SARS-CoV-2 virus was capable of not only infecting human beta cells, but was also able to replicate inside of them, allowing it to invade other cells, too. Those beta cells are important-they’re responsible for secreting insulin-and in type 1 diabetes, it’s those beta cells that don’t secrete enough insulin for the body to use. (Note: the NIH blog and one NIH-funded studies only referenced type 1 diabetes).

Going off of that information, both NIH-funded studies found and confirmed infection of pancreatic beta cells in autopsy samples from people who died from COVID-19-and one of the studies suggests that SARS-CoV-2 may “preferentially infect” those insulin-producing cells.

It’s important to reiterate that the two NIH-funded studies were conducted via autopsy in people who had already died of COVID-19 to see exactly how a SARS-CoV-2 infection could affect pancreatic cells-specifically the insulin-producing beta cells.

As of right now, much more research is needed “to understand how SARS-CoV-2 reaches the pancreas and what role the immune system might play in the resulting damage,” the NIH says.

And although these findings aren’t solidified as of yet, they still have an important function for doctors and patients: For one, the information may lead physicians to look more closely at COVID-19 patients, especially those with “long-hauler” symptoms, says Dr. Schaffner. And, as usual, they serve as yet another reminder to take this virus seriously, and to get vaccinated (and encourage others to do the same) to protect family members, friends, and strangers alike.