Can COVID-19 Cause Diabetes? Here's What You Need to Know
More research needs to be done, but experts say the link between the two is "troubling."
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.
The news comes from the National Institutes of Health (NIH), which addressed the new findings in a Director's Blog post published Tuesday. The studies, both NIH-supported pre-proof studies available in the journal Cell Metabolism, confirm "that SARS-CoV-2 can target and impair the body's insulin-producing cells." This, as a result, can lead to diabetes.
But it's not just those two studies. The new findings come months after data published in a Letter to the Editor in Diabetes, Obesity, and Metabolism: A Journal of Pharmacology and Therapeutics also found a link between COVID-19 infections and new cases of diabetes.
For a world that's been ravaged by COVID-19 for more than a year now—and since, to date, the virus has infected 175 million people worldwide—this is big news. "Obviously, having COVID is much more than whether you live or die," Thomas Russo, MD, professor and chief of infectious disease at the University at Buffalo in New York, tells Health. "People need to think more in terms of the long-term potential health consequences of getting infected. If you get diabetes, that will affect you for the rest of your life."
"This nasty virus just got nastier," William Schaffner, MD, an infectious disease specialist and professor at the Vanderbilt University School of Medicine, tells Health. "Now, the data is much more secure that this virus can get into various organ systems and cause damage."
Research is still ongoing to further solidify this link between COVID-19 infections and new diabetes diagnoses—but here's what we know so far.
First, what is diabetes?
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.
Diabetes is also broken up into two main types: type 1 diabetes, which is when the body doesn't make insulin due to the immune system attacking and destroying insulin-making cells in the pancreas; and type 2 diabetes, which is when your body does not make or use insulin well. Both types of diabetes have no cure, but the disease can be managed.
What does the research say about COVID-19 leading to diabetes?
Let's start from the beginning: The Letter to the Editor 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."
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.
That's not all: The new research also found that coronavirus infections could also change clusters of cells known as islets in the pancreas, which contain the beta cells. Specifically, both teams of researchers found that the pancreatic islet tissue showed reduced production and release of insulin following a coronavirus infection—and sometimes, infection also led to the death of some beta cells. Even some remaining beta cells were found to go through "transdifferentiation" or "reprogramming" in which they begin producing less insulin and more glucagon (another hormone that controls glucose levels)—something that, while not yet confirmed, could "worsen insulin deficiency and raise blood glucose levels," per the NIH.
What else do you need to know about COVID-19 and diabetes?
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. That means this research was looking at the way that COVID-19 impacts those cells, which is different than actually diagnosing a type of diabetes, infectious disease expert Amesh A. Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security, tells Health.
There are also still quite a few unknowns here, including what type of diabetes might be at play here (though Dr. Adalja says this may be "somewhat more like a type 1 than a type 2") and if the severity of coronavirus infection dictates whether (or how much) pancreatic tissue and beta cells are affected.
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. Dr. Adalja adds that the next probable step in studying COVID-19's link to diabetes is to match these study findings (which, again, were conducted via autopsy in a lab) with "actual clinical development of diabetes in surviving patients."
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.
The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDC, WHO, and their local public health department as resources.
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